WO2009119411A1 - Process for producing zno single crystal, self-supporting zno single-crystal wafer obtained by the same, self-supporting wafer of mg-containing zno mixed single crystal, and process for producing mg-containing zno mixed single crystal for use in the same - Google Patents

Process for producing zno single crystal, self-supporting zno single-crystal wafer obtained by the same, self-supporting wafer of mg-containing zno mixed single crystal, and process for producing mg-containing zno mixed single crystal for use in the same Download PDF

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WO2009119411A1
WO2009119411A1 PCT/JP2009/055301 JP2009055301W WO2009119411A1 WO 2009119411 A1 WO2009119411 A1 WO 2009119411A1 JP 2009055301 W JP2009055301 W JP 2009055301W WO 2009119411 A1 WO2009119411 A1 WO 2009119411A1
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single crystal
zno
crystal
mixed
self
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PCT/JP2009/055301
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French (fr)
Japanese (ja)
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関和　秀幸
純 小林
美幸 宮本
大橋　直樹
勲 坂口
芳樹 和田
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三菱瓦斯化学株式会社
独立行政法人物質・材料研究機構
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Priority claimed from JP2008080629A external-priority patent/JP2009234824A/en
Priority claimed from JP2008080639A external-priority patent/JP2009234825A/en
Application filed by 三菱瓦斯化学株式会社, 独立行政法人物質・材料研究機構 filed Critical 三菱瓦斯化学株式会社
Priority to EP09726041.8A priority Critical patent/EP2267193A4/en
Priority to US12/934,835 priority patent/US20110024742A1/en
Priority to CN2009801101420A priority patent/CN101978102A/en
Publication of WO2009119411A1 publication Critical patent/WO2009119411A1/en

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    • H—ELECTRICITY
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
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    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
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    • H01L21/02623—Liquid deposition
    • H01L21/02625—Liquid deposition using melted materials
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B19/00—Liquid-phase epitaxial-layer growth
    • C30B19/02—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B9/00—Single-crystal growth from melt solutions using molten solvents
    • C30B9/04—Single-crystal growth from melt solutions using molten solvents by cooling of the solution
    • C30B9/08—Single-crystal growth from melt solutions using molten solvents by cooling of the solution using other solvents
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
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    • H01L21/02565—Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02628—Liquid deposition using solutions

Definitions

  • the present invention relates to a ZnO-based semiconductor material, and more particularly to a method for producing a ZnO single crystal useful in the fields of optics and electric / electronic industry and a free-standing ZnO single crystal wafer obtained thereby. Furthermore, the present invention relates to a self-supporting Mg-containing ZnO mixed crystal single crystal wafer having high composition uniformity that is particularly useful in the fields of optics and electric / electronic industries, and a method for producing an Mg-containing ZnO mixed crystal single crystal used therefor.
  • Si, GaAs, GaN, and the like have been used for optical and electronic devices having various functions. Recently, light-emitting devices and electronic devices using GaN have been actively developed. On the other hand, focusing on oxides, ZnO has been used for varistors, gas sensors, sunscreens, etc. Recently, optical elements, electronic elements, piezoelectric elements, transparent electrodes, etc., due to its optical characteristics, electronic element characteristics and piezoelectric characteristics. Has been attracting attention. In particular, it is known that ZnO has a direct transition type band gap of 3.3 to 3.4 eV like GaN, and emits 380 nm ultraviolet light, and emits light of a short wavelength from blue to ultraviolet region. Research and development for applications and applications for semiconductors for light-emitting elements that emit light has become active.
  • Patent Document 1 discloses that a semiconductor having a high band density and a semiconductor having a high band density and a semiconductor having a low band gap and a high electron mobility are stacked to form an electron from a semiconductor having a high band density.
  • a semiconductor material that satisfies both a high electron concentration and a high electron mobility is disclosed by inducing charge transfer to a semiconductor with high mobility and moving electrons through a layer with high mobility.
  • a II-VI group semiconductor mixed crystal Zn 1-x Mg x O having a wide band gap is obtained by a pulse laser deposition method at a growth temperature of 600 ° C. It has been shown that a wider band gap than ZnO can be obtained by adjusting x (A. Ohtomo et.al, Applied Physics Letters, Vol.72, No.19, 11 May 1998, 2466-2468) Patent Document 1).
  • x A. Ohtomo et.al, Applied Physics Letters, Vol.72, No.19, 11 May 1998, 2466-2468
  • Patent Document 1 In consideration of application to a light emitting element, it is necessary to adopt a double hetero structure in order to increase the light emission efficiency. By employing the above structure, carrier confinement and light extraction efficiency are improved, and light emission efficiency is improved.
  • High crystallinity is required to exhibit the electronic element characteristics and optical element characteristics of the ZnO-based semiconductor single crystal.
  • a ZnO-based semiconductor single crystal has been grown by a vapor phase growth method using an insulating substrate such as ZnO, ScAlMgO 4 and sapphire.
  • an insulating substrate such as ZnO, ScAlMgO 4 and sapphire.
  • a commercially available ZnO single crystal substrate is grown by a hydrothermal synthesis method, and it is inevitable that Li based on LiOH used as a mineralizer is mixed into the ZnO single crystal.
  • Patent Document 2 Japanese Patent Laid-Open No. 2007-204324
  • annealing at 1100 ° C. for 1 to 2 hours is about 8.4 ⁇ 10 16 pieces / cm 3 to 2.0 ⁇ 10 17 pieces / cm 3
  • annealing at 1300 ° C. for about 2 hours is 9 ⁇ . It is described that the Li concentration in ZnO can be reduced to about 10 14 pieces / cm 3 .
  • the ZnO-based semiconductor single crystal can be made self-supporting by growing a thick ZnO-based semiconductor single crystal and then removing the hydrothermally-synthesized substrate by polishing or etching, Li Impurity contamination can be significantly reduced. Furthermore, if an impurity capable of imparting conductivity can be doped at the same time and become self-supporting, it is possible to provide a self-supporting conductive ZnO single crystal wafer having a low Li concentration and conductivity.
  • Patent Document 3 International Publication No. 2007/100146 pamphlet
  • the crystal layer is grown by liquid phase epitaxial (LPE) using zinc oxide A-1 as a substrate (hereinafter, the grown crystal layer may be referred to as “LPE layer”).
  • LPE layer liquid phase epitaxial
  • the B-3 part in which the Li concentration in the hydrothermal synthesis substrate is decreased and the B-1 part having the original Li concentration are obtained.
  • the LPE layer B-2 is grown, Li in the hydrothermal synthesis substrate diffuses in the initially grown portion, and a B-4 layer having an increased Li concentration is formed in the LPE growth film.
  • the obtained self-supporting substrate is composed of the LPE layer B-2 and the Li diffusion layer B-4 that should be originally obtained.
  • the B-4 layer having a slightly higher Li concentration than B-2 caused the device characteristics to become unstable.
  • the growth rate is low, and thick film growth is extremely difficult.
  • the growth rate can be controlled by controlling the degree of supersaturation, and a relatively high growth rate is possible.
  • an insulating material is often used for a substrate in vapor phase growth and liquid phase growth.
  • an electronic element or an optical element using a ZnO-based mixed crystal single crystal it is necessary to devise such as forming electrodes in the same direction.
  • the manufacturing process of the electronic element and the optical element is complicated, resulting in high cost, and the problem is that the electric field is concentrated on a part of the n-type contact layer (n + ) layer and the lifetime of the element is shortened. There was a point.
  • an insulating substrate is used to grow a thick ZnO film with electrical conductivity and the unnecessary insulating substrate can be removed by polishing, etc.
  • electrodes can be formed on the front and back sides, and device characteristics can be obtained even in the device fabrication process. In addition, it can be expected to improve performance in terms of life (see Fig. 2).
  • a ZnO-based semiconductor single crystal and a laminate thereof as a study of the above materials are grown by a vapor phase growth method that is non-thermal equilibrium growth (for example, Japanese Patent Application Laid-Open No. 2003-046081 (Patent Document 4)). Mixing of growth defects is unavoidable, and the crystal quality is not sufficient.
  • a field effect transistor, a pn junction light emitting element, or the like which is an example of a conventional semiconductor element, the crystallinity is greatly involved in optical characteristics and semiconductor characteristics.
  • the crystal quality of the crystal by the vapor phase growth method is not sufficient, there is a problem that the original performance cannot be sufficiently exhibited. Therefore, in order to apply and develop the above-mentioned uses, it is an important issue to establish a manufacturing method of ZnO single crystal with high crystal quality.
  • Non-patent Document 2 In the case of a ZnO-based semiconductor layer, n-type growth is relatively easy, but considering that p-type growth is difficult, it is difficult to grow a p-type layer with -c plane growth. There was a point.
  • the inventors have devised the composition of the solute and the solvent to grow a Mg-containing ZnO mixed crystal single crystal by a liquid phase epitaxial (LPE) growth method. succeeded in. However, simply removing the substrate after growing the mixed crystal layer reveals a slight band gap difference between the front and back surfaces of the obtained self-supporting Mg-containing ZnO mixed single crystal, and the assumed light transmission The rate could not be obtained.
  • LPE liquid phase epitaxial
  • the present inventors diligently studied the above problems and found that there are the following problems.
  • the description will be made again with reference to FIG.
  • the structure is a B-1 portion in which the state as pure zinc oxide is maintained and a B-3 portion in which Mg is diffused.
  • Mg is diffused from the initially grown portion to the substrate, so that the diffusion layer B-3 is formed on the substrate side.
  • a diffusion layer B-4 having a reduced Mg concentration is formed.
  • the self-supporting Mg-containing ZnO mixed crystal single crystal is composed of the mixed crystal layer B-2 and the diffusion layer B-4 that should originally be obtained.
  • the diffusion layer B-4 that should originally be obtained.
  • an optical element or an electronic element was formed using this as a near-ultraviolet transparent substrate, sufficient light transmittance could not be obtained due to B-4 having a slightly narrower band gap than B-2.
  • Li is contained as an impurity in the hydrothermal synthesis substrate used for LPE growth, and in particular, a Li impurity concentrated layer is formed on the substrate surface. Therefore, a Li diffusion layer was formed in the B-4 layer, and the composition was nonuniform.
  • a substrate that is lattice-matched with ZnO to be grown and is transparent to LED light is optimal in terms of light extraction efficiency.
  • a self-supporting Mg-containing ZnO mixed crystal single crystal composed only of the Mg-containing ZnO mixed crystal single crystal and having a band gap larger than that of ZnO is suitable.
  • Non-patent Document 2 Non-patent Document 2
  • n-type growth is relatively easy, but considering that p-type growth is difficult, it is difficult to grow a p-type layer with -c plane growth.
  • the -c plane growth film is an oxygen surface, there are problems that the etching rate with acid is fast and difficult to control, and that etching with high flatness is difficult.
  • the ZnO hydrothermal synthesis substrate is mixed with Li based on the mineralizer, and when this is used as a substrate for the LPE growth of ZnO single crystal, there is a problem that Li diffuses to the LPE growth film side. Furthermore, after growing a thick ZnO single crystal using the LPE growth method, Li diffuses to the growth film side even if the substrate portion is removed by polishing or etching, so that the LPE growth film becomes self-supporting. However, there was a problem of destabilization of device characteristics based on Li.
  • the present inventors diligently studied to obtain a ZnO-based mixed crystal single crystal that can be self-supported and a laminate thereof. As a result, only by removing the substrate after growing the mixed crystal layer, a slight band gap difference is found between the front and back surfaces of the obtained self-standing Mg-containing ZnO mixed single crystal, and the assumed light transmittance is reduced. It has been found that there is a difference in impurity concentration between the front surface and the back surface of the free-standing Mg-containing ZnO mixed single crystal, and this may cause alteration of optical properties and electrical properties. It was. This method has the following problems. This will be described with reference to FIG.
  • the mixed crystal As a substrate, zinc oxide having a structure in which a contamination layer produced by polishing or surface treatment on the surface of high-quality crystalline A-2, or A-3 which is a crystalline deterioration layer is present is present. Since the mixed crystal is grown by LPE, after the growth, the D-3 portion which is the interface portion on the substrate side becomes a layer in which Mg diffused from the growth layer and impurities diffused from the contamination layer exist. Further, the hydrothermal synthesis substrate after the LPE growth is composed of a high quality zinc oxide layer D-1 and a diffusion / contamination layer D-3. On the other hand, when the mixed crystal layer is grown, Mg diffuses from the initially grown portion to the hydrothermal synthesis substrate, and impurities diffuse from the contaminated layer A-3 of the substrate.
  • the self-standing Mg-containing ZnO mixed crystal single crystal has a mixed crystal layer E ⁇ in which the Li contamination level to be originally obtained is maintained at 1 ⁇ 10 15 pieces / cm 3 or less. 2 and a diffusion layer E-4 having a Li concentration exceeding that and a Mg concentration lower than that of the E-2 layer.
  • the band gap was slightly narrowed compared to E-2, and due to E-4 having a large amount of Li, sufficient light transmittance could not be obtained. .
  • ZnO as a solute and a solvent are mixed and melted, and then the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is continuously formed. And a step of growing the ZnO single crystal on the seed crystal substrate by pulling up periodically or intermittently.
  • the solvent is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO.
  • the second embodiment of the present invention is a self-supporting ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment of the present invention, and has a film thickness of 100 ⁇ m or more. It is a free-standing ZnO single crystal wafer characterized.
  • self-supporting means that the seed crystal substrate used for growth is removed by polishing and / or etching and consists of only a growth layer.
  • continuous means that the pulling rate is constant in the step of pulling up the seed crystal substrate, and the term “intermittent” means that the pulling rate changes in the step of pulling up the seed crystal substrate. It means to do.
  • the term “solute” refers to a substance that dissolves in a solvent when a solution is made, and the term “solvent” refers to a substance that becomes a medium of a substance that is dissolved when a solution is made.
  • the third embodiment of the present invention has a plate-like shape with a thickness of 50 ⁇ m or more, has a uniform chemical composition of Zn and Mg in both the thickness direction of the plate and the in-plane direction, and
  • the self-standing Mg-containing ZnO mixed single crystal wafer is characterized in that at least one of the front and back surfaces has flatness capable of epitaxial growth.
  • the fourth embodiment of the present invention includes a step of directly contacting a seed crystal substrate with the obtained melt after mixing and melting ZnO and MgO, which are solutes, and a solvent, and the seed crystal substrate.
  • the fifth embodiment of the present invention is a self-supporting Mg-containing ZnO mixed single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment, and has a thickness of 50 ⁇ m.
  • Mg-containing ZnO mixed crystal single crystal refers to a single crystal having a composition of Zn 1-x Mg x O (0 ⁇ x ⁇ 0.15).
  • a thick ZnO single crystal can be obtained.
  • the seed crystal substrate is removed by polishing or etching, and the -c plane side of the single crystal subjected to liquid phase epitaxial growth is polished or etched to obtain a freestanding ZnO single crystal having a low Li concentration.
  • the obtained free-standing ZnO single crystal is suitably used as a wafer as it is or as a seed crystal substrate of a ZnO-based mixed crystal single crystal.
  • the free-standing ZnO single crystal wafer which is a preferred embodiment of the present invention has high crystallinity and can control the carrier concentration while maintaining high carrier mobility.
  • both the + c plane and the ⁇ c plane can be used as the surface of the device fabrication substrate, and a growth plane suitable for the target device can be selected.
  • the band gap is wide compared with ZnO, and the self-supporting Mg containing ZnO type mixed crystal single crystal which ensured the transparency with respect to near ultraviolet from visible light is obtained. Since the obtained self-supporting Mg-containing ZnO-based mixed crystal single crystal is a single crystal, it can realize high mobility that cannot be obtained by polycrystal, and is preferably used as a wafer.
  • the self-supporting Mg-containing ZnO mixed single crystal wafer of a preferred embodiment of the present invention has high crystallinity and can control carriers while maintaining high carrier mobility.
  • the composition of Zn and Mg becomes uniform, and the transmittance in the near ultraviolet region can be increased. Therefore, the light extraction efficiency of light emitting elements such as LEDs using ZnO Can be high.
  • Li diffusion from the substrate can be reduced, and unstable operation during device operation can be suppressed, and at least one selected from the group consisting of Al, Ga, In, H, and F is included.
  • Can provide electrical conductivity.
  • both the + c plane and the ⁇ c plane can be used for the device fabrication substrate surface, and a growth plane suitable for the target device can be selected. From the above characteristics, it can be used as a transparent TFT transparent to visible light.
  • the self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer of the present invention can be used for electronic elements and optical elements that are expected to develop in the future.
  • FIG. 1 is a schematic cross-sectional view for explaining problems in producing a self-supporting Mg-containing ZnO mixed single crystal.
  • FIG. 2 is a configuration diagram showing a conventional element structure and an element structure using an Mg-containing ZnO mixed single crystal obtained by the present invention.
  • FIG. 3 is a schematic cross-sectional view for explaining problems in the production of a self-supporting Mg-containing ZnO mixed single crystal.
  • FIG. 4 is a block diagram of the furnace used in the examples and comparative examples of the present invention.
  • ZnO as a solute and a solvent are mixed and melted, and then the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is continuously formed. And a step of growing the ZnO single crystal on the seed crystal substrate by pulling up periodically or intermittently.
  • a method for producing a ZnO single crystal by a liquid phase epitaxial growth method is described in detail.
  • a thick film growth of the ZnO single crystal is required.
  • the thickness is at least about 50 ⁇ m.
  • a growth film thickness of about 100 ⁇ m or more is required in consideration of the polishing margin on the front and back surfaces.
  • the present inventors have conducted intensive research.
  • the Pt jig is brought into contact with the melt by continuously or intermittently pulling up the Pt jig holding the seed crystal substrate during growth.
  • the shaft pulling method either continuous or intermittent can be adopted, but continuous shaft pulling is superior in terms of stable growth.
  • the speed V for continuously pulling up the seed crystal substrate is preferably 2 ⁇ m / hr or more and 50 ⁇ m / hr or less. More preferably, it is 4 ⁇ m / hr or more and 20 ⁇ m / hr or less, and further preferably 6 ⁇ m / hr or more and 10 ⁇ m / hr or less. If it is less than 2 ⁇ m / hr, the effect of reducing the entrainment of flux by pulling up the shaft is small, and if it exceeds 50 ⁇ m / hr, the substrate may be separated from the melt surface. When the seed crystal substrate is pulled up intermittently, the average speed is preferably within the above range.
  • the average speed v for intermittently pulling up the seed crystal substrate is preferably 2 ⁇ m / hr or more and 50 ⁇ m / hr or less, more preferably 4 ⁇ m / hr or more and 20 ⁇ m / hr or less, and further preferably 6 ⁇ m / hr or more. 10 ⁇ m / hr or less.
  • the solvent that can be used is not particularly limited as long as it can melt the solute ZnO, but is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO.
  • a step of bringing a seed crystal substrate into direct contact with the obtained melt a step of growing the ZnO single crystal on the seed crystal substrate by pulling the seed crystal substrate continuously or intermittently, and a method for producing a ZnO single crystal by a liquid phase epitaxial growth method.
  • the mixing ratio of ZnO as a solute and PbO and Bi 2 O 3 as solvents is more preferably a solute concentration of 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature may increase.
  • a seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal And a step of growing the ZnO single crystal on the seed crystal substrate by pulling the substrate continuously or intermittently.
  • the amount of evaporation of the solvents PbF 2 and PbO can be suppressed, and as a result, fluctuations in the solute concentration are reduced.
  • a ZnO single crystal can be stably grown.
  • the mixing ratio of ZnO as the solute and PbF 2 and PbO as the solvent is more preferable when the solute is 5 to 10 mol%. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the temperature at which the solute component is dissolved increases and the amount of solvent evaporation may increase. In the present invention, a liquid phase growth method is used.
  • this method does not require a vacuum system, so that it is possible to produce a ZnO single crystal at low cost and to grow a ZnO single crystal having high crystallinity because of thermal equilibrium growth. Can be made. Further, by controlling the degree of supersaturation, the growth rate can be controlled, and a relatively high growth rate can be realized.
  • the ZnO single crystal contains a small amount of a different element.
  • ZnO can exhibit and change its characteristics by doping with different elements.
  • Li, Na, K, Cs, Rb, Be, Ca, Sr, Ba, Cu, Ag, N, P, As, Sb, Bi, B, Tl, Cl, Br, I, Mn One or more selected from the group consisting of Fe, Co, Ni, Cd, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and a lanthanoid element are added.
  • the addition amount is 20 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, with respect to ZnO used as a solute.
  • elements there are p-type semiconductors, n-type semiconductors, magnetic semiconductors, conductivity control, varistor applications, piezoelectric body applications, electroluminescent elements, and transparent TFTs.
  • a ZnO single crystal is used as a seed crystal substrate that is a growth substrate.
  • a substrate for ZnO single crystal growth any substrate can be used as long as it has a crystal structure similar to ZnO and the grown thin film does not react with the substrate. Examples thereof include sapphire, LiGaO 2 , LiAlO 2 , LiNbO 3 , LiTaO 3 , ScAlMgO 4 , GaN, and ZnO.
  • the target single crystal in the present invention is a ZnO single crystal
  • homoepitaxial growth using a ZnO substrate having a high degree of lattice matching between the substrate and the grown crystal reduces crystallinity, distortion, and warpage of the grown film. And it is preferable in terms of reducing the amount of impurity diffusion from the substrate.
  • the growth orientation of the ZnO single crystal is the + c plane.
  • the seed crystal substrate used for the growth can be made independent by polishing or etching.
  • the Li diffusion layer from the substrate side can be removed by removing at least 10 ⁇ m, preferably 20 ⁇ m or more, on the ⁇ c plane side close to the growth substrate.
  • any method of polishing or etching can be adopted, but grinding + polishing which allows easy film thickness management is preferable.
  • a ZnO single crystal is grown on a hydrothermal synthesis substrate.
  • a film thickness of about 100 ⁇ m is required at the growth stage.
  • the substrate side is fixed to the ceramic plate by WAX, and the liquid phase epitaxial growth surface can be flattened by a grinder.
  • the LPE surface side (+ c surface) may be replaced with a ceramic plate, and the substrate thickness may be ground and removed by a grinder to obtain only a liquid phase epitaxial growth film, and polishing may be performed by lapping and polishing the front and back surfaces.
  • it is possible to remove the Li diffusion layer from the hydrothermal synthesis substrate by polishing the hydrothermal synthesis substrate side of the LPE growth film preferably at 10 ⁇ m, more preferably 20 ⁇ m or more.
  • the ZnO single crystal contains one or more selected from the group consisting of Al, Ga, In, H and F.
  • the substrate used for growth is removed by polishing, etching, or the like, a self-supporting conductive substrate is formed, and electrodes can be formed on the front and back of the electronic element and the optical element.
  • the second embodiment of the present invention is a self-supporting ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment of the present invention, and has a film thickness of 100 ⁇ m or more. It is a free-standing ZnO single crystal wafer characterized. If the thickness is less than 100 ⁇ m, 50 ⁇ m cannot be ensured as the thickness after polishing, and it is difficult to use in subsequent device processes. The upper limit of the thickness is not specified, but if it exceeds 500 ⁇ m, the growth time becomes longer.
  • the Li concentration of the free-standing ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment is uniform in the in-plane direction and the thickness direction of the wafer. And, Preferably it is 1 * 10 ⁇ 15 > piece / cm ⁇ 3 > or less, More preferably, it is 1 * 10 ⁇ 14 > piece / cm ⁇ 3 > or less.
  • the Li concentration is uniform at 1 ⁇ 10 15 pieces / cm 3 or less
  • the Li concentration that destabilizes the device operation is 1 ⁇ 10 15 pieces / cm 3 or less in the entire self-supporting film.
  • the uniformity of the Li concentration can be obtained as follows.
  • the Li concentration uniformity in the front and back surfaces was further measured.
  • the Li concentration uniformity in the film thickness direction can be determined by measuring the Li concentration by dynamics SIMS.
  • the flatness of at least one surface of the free-standing ZnO single crystal wafer may be such that it can be epitaxially grown.
  • the surface roughness Ra of 50 ⁇ m square at an arbitrary position of the ZnO single crystal wafer is preferably 0.5 nm or less, more preferably 0.3 nm or less. If it exceeds 0.5 nm, the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable.
  • the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping.
  • the surface roughness Ra can be measured by using an atomic force microscope (AFM) with respect to a 50 ⁇ m square of the free-standing film central part.
  • AFM atomic force microscope
  • the free-standing ZnO single crystal wafer preferably contains Ga, has a carrier concentration of 2.0 ⁇ 10 17 pieces / cm 3 to 1.0 ⁇ 10 19 pieces / cm 3 , and
  • the Li concentration is preferably 1 ⁇ 10 15 atoms / cm 3 or less, more preferably 1 ⁇ 10 14 atoms / cm 3 or less.
  • the self-supporting ZnO single crystal wafer contains Al and has a carrier concentration of 2.0 ⁇ 10 17 pieces / cm 3 to 1.0 ⁇ 10 19 pieces / cm 3 , And it is preferable that Li concentration is 1 * 10 ⁇ 15 > piece / cm ⁇ 3 > or less, More preferably, it is 1 * 10 ⁇ 14 > piece / cm ⁇ 3 > or less.
  • the self-supporting ZnO single crystal wafer contains In and has a carrier concentration of 2.0 ⁇ 10 17 pieces / cm 3 to 3.5 ⁇ 10 17 pieces / cm 3 , And it is preferable that Li concentration is 1 * 10 ⁇ 15 > piece / cm ⁇ 3 > or less, More preferably, it is 1 * 10 ⁇ 14 > piece / cm ⁇ 3 > or less.
  • carrier concentration and “carrier mobility” can be measured at room temperature by the Van Der Pauw method using a Hall effect / specific resistance measuring device manufactured by Toyo Technica.
  • the third embodiment of the present invention has a plate-like shape with a thickness of 50 ⁇ m or more, has a uniform chemical composition of Zn and Mg in both the thickness direction and the in-plane direction of the plate, A self-standing Mg-containing ZnO mixed single crystal wafer characterized in that at least one of the back surfaces has flatness that can be used as a substrate for epitaxial growth.
  • a thickness of less than 50 ⁇ m is not preferable because it becomes difficult to handle.
  • the upper limit of the thickness is not particularly limited, but if it exceeds 500 ⁇ m, the growth time becomes long.
  • the composition uniformity in the film thickness direction and in-plane direction of the self-supporting Mg-containing ZnO mixed single crystal wafer is preferably within ⁇ 10%, more preferably within ⁇ 5%. If the composition uniformity exceeds ⁇ 10%, the transmittance in the near ultraviolet region decreases, which is not preferable.
  • the composition uniformity in the in-plane direction is evaluated by the uniformity of the Mg / (Zn + Mg) composition on the front and back surfaces of the self-supporting Mg-containing ZnO mixed single crystal wafer. It can obtain
  • composition uniformity in the film thickness direction is evaluated by the uniformity of the Mg / (Zn + Mg) composition in the film thickness direction of the self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer. It can be obtained by measuring CL (Cathode Luminescence; electron beam excitation emission spectrum measurement) emission wavelength distribution of a section cut perpendicular to the c-plane.
  • CL Cathode Luminescence; electron beam excitation emission spectrum measurement
  • the flatness of at least one of the front and back surfaces of the self-supporting Mg-containing ZnO mixed crystal single crystal wafer may be such that epitaxial growth is possible.
  • the surface roughness Ra of 50 ⁇ m square is preferably 0.5 nm or less, more preferably 0.3 nm or less, at an arbitrary position of the self-supporting Mg-containing ZnO mixed single crystal wafer. If it exceeds 0.5 nm, the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable.
  • the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping.
  • the surface roughness Ra can be measured by using an atomic force microscope (AFM) with respect to a 50 ⁇ m square of the free-standing film central part.
  • AFM atomic force microscope
  • a preferred embodiment of the present invention is a self-standing Mg-containing ZnO mixed single crystal wafer having a band gap (Eg) value that is uniform in the in-plane direction and the thickness direction of the wafer and exceeds 3.30 eV. is there.
  • the uniformity of the band gap (Eg) value can be determined from the PL and CL emission wavelengths, and the band gap (Eg) value is preferably within ⁇ 6%, more preferably within ⁇ 3%.
  • the band gap of a ZnO-based mixed crystal single crystal it can be realized by mixing ZnO and MgO or BeO. However, considering toxicity and the like, it is preferable to mix MgO. If the band gap of the ZnO-based mixed crystal single crystal is less than 3.30 eV, the MgO mixed crystallization rate is low, which is not preferable.
  • the band gap (Eg) can be determined by measuring the PL and CL emission wavelengths of the Mg-containing ZnO mixed crystal single crystal obtained by the present invention and using the following equation.
  • Eg [eV] 1.24 / PL (CL) emission wavelength [nm] * 1000
  • the method for measuring the PL emission wavelength is not particularly limited.
  • the method for measuring the CL emission wavelength is not particularly limited, but in the present invention, it is based on a value measured at room temperature using a 5 KeV electron beam as an excitation source.
  • the self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer contains one or more selected from the group consisting of Al, Ga, In, H and F.
  • the substrate used for growth is removed by polishing, etching, or the like, electrodes can be formed on the front and back surfaces of the electronic element or optical element. Accordingly, it is possible to provide a Mg-containing ZnO mixed single crystal having self-supporting conductivity.
  • the self-supporting Mg-containing ZnO mixed single crystal having conductivity is transparent to LED light in a ZnO-LED device, and can be a lattice-matched substrate having conductivity.
  • the Li concentration is uniform in the in-plane direction and the thickness direction of the wafer, and is preferably 1 ⁇ 10 15 pieces / cm 3 or less, more preferably 1 ⁇ 10 14 pieces.
  • This is a self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer of / cm 3 or less.
  • the Li concentration that destabilizes the device operation is 1 ⁇ 10 15 pieces / cm 3 or less in the entire self-supporting film.
  • the uniformity of the Li concentration can be obtained as follows.
  • the Li concentration uniformity in the film thickness direction can be determined by measuring the Li concentration by dynamics SIMS.
  • the dynamic SIMS analysis is performed under the conditions of primary ion species; O 2+ , primary ion acceleration voltage; 8 KeV, measurement temperature;
  • the hydrothermal synthetic substrate used at the time of liquid phase epitaxial growth contains about 1 ⁇ 10 15 to 1 ⁇ 10 17 pieces / cm 3 of Li.
  • the only way to achieve high crystal growth by the LPE growth method is to use a single crystal grown by hydrothermal synthesis.
  • the crystal quality is not necessarily high quality, and at present, only a hydrothermally synthesized ZnO single crystal is a functional substrate material. Therefore, it is necessary to take measures against the Li impurity that is characteristic of it.
  • the step of polishing the LPE growth film on the hydrothermal synthesis substrate side is preferably 10 ⁇ m, more preferably 20 ⁇ m or more.
  • the synthetic substrate side is preferably polished at 10 ⁇ m, more preferably 20 ⁇ m or more.
  • the substrate may be thermally diffused from the Li concentrated layer on the substrate surface.
  • the growth back surface side (-c surface) of the LPE growth film on the hydrothermal synthesis substrate side is polished preferably by 10 ⁇ m or more, more preferably by 20 ⁇ m or more, Li in the liquid phase epitaxial growth film can be obtained. It was found that the concentration was 1 ⁇ 10 15 pieces / cm 3 or less. Moreover, if it is used for the Mg-containing ZnO mixed crystal single crystal wafer obtained thereby, it becomes possible to suppress destabilization of device characteristics based on Li.
  • the fourth embodiment of the present invention includes a step of directly contacting a seed crystal substrate with the obtained melt after mixing and melting ZnO and MgO, which are solutes, and a solvent, and the seed crystal substrate. And continuously growing the Mg-containing ZnO mixed crystal single crystal on the seed crystal substrate by continuously or intermittently pulling the Mg-containing ZnO mixed crystal single crystal by the liquid phase epitaxial growth method. It is a manufacturing method of a crystal.
  • a thick film growth of the Mg-containing ZnO mixed crystal single crystal is required.
  • a growth film thickness of about 100 ⁇ m or more is required in consideration of the polishing margin on the front and back surfaces.
  • the present inventors mixed ZnO and MgO as solutes so far with PbO and Bi 2 O 3 as solvents and melted them, and then contacted the seed crystal or the substrate directly with the obtained melt.
  • the obtained melt The Mg-containing ZnO mixed crystal single crystal having a film thickness of 100 ⁇ m or more can be grown by liquid phase epitaxy by directly contacting the seed crystal or the substrate and appropriately adjusting the growth time and the temperature drop rate during the growth. I found out that I can do it.
  • the hydrothermal synthesis substrate is held using a Pt jig and the substrate surface is brought into contact with the melt surface for epitaxial growth.
  • the present inventors have conducted intensive research. As a result, the Pt jig / tool holding the substrate during the growth is pulled up continuously or intermittently, thereby reducing the time for the Pt jig to contact the melt. As a result of the reduction, it was found that the flux mixing into the film can be reduced, and as a result, the generation of cracks during growth and during polishing / etching can be suppressed.
  • the shaft pulling method either continuous or intermittent can be adopted, but continuous shaft pulling is superior in terms of stable growth.
  • the speed V for continuously pulling up the seed crystal substrate is preferably 2 ⁇ m / hr or more and 50 ⁇ m / hr or less. More preferably, it is 4 ⁇ m / hr or more and 20 ⁇ m / hr or less, and further preferably 6 ⁇ m / hr or more and 10 ⁇ m / hr or less. If it is less than 2 ⁇ m / hr, the effect of reducing the entrainment of flux by pulling up the shaft is small, and if it exceeds 50 ⁇ m / hr, the substrate may be separated from the melt surface. When the seed crystal substrate is pulled up intermittently, the average speed is preferably within the above range.
  • the average speed v for intermittently pulling up the seed crystal substrate is preferably 2 ⁇ m / hr or more and 50 ⁇ m / hr or less, more preferably 4 ⁇ m / hr or more and 20 ⁇ m / hr or less, and further preferably 6 ⁇ m / hr or more. 10 ⁇ m / hr or less.
  • the solvent that can be used is not particularly limited as long as it can melt ZnO and MgO as solutes, but is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO.
  • the PbO and Bi 2 O 3 mixed solvent having the above mixing ratio is preferable.
  • the mixing ratio of the solute converted to ZnO and the solvents PbO and Bi 2 O 3 is more preferably a solute concentration of 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature increases and the amount of solvent evaporation may increase.
  • a ZnO mixed crystal single crystal can be stably grown.
  • the mixing ratio of the solutes ZnO and MgO to the solvents PbF 2 and PbO is more preferable when the solute converted to ZnO alone is 5 to 10 mol%. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the temperature at which the solute component is dissolved increases and the amount of solvent evaporation may increase.
  • a liquid phase growth method is used. Unlike the vapor phase growth method, this method does not require a vacuum system.
  • a ZnO mixed crystal single crystal can be manufactured at a low cost, and since it is thermal equilibrium growth, it has a high crystallinity.
  • Mixed crystal single crystals can be grown. Further, by controlling the degree of supersaturation, the growth rate can be controlled, and a relatively high growth rate can be realized.
  • the Mg-containing ZnO mixed single crystal contains a small amount of different elements.
  • ZnO can exhibit and change its characteristics by doping with different elements.
  • One or more selected from the group consisting of Fe, Co, Ni, Cd, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and a lanthanoid element are added.
  • the addition amount is 20 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, with respect to ZnO used as a solute.
  • elements there are p-type semiconductors, n-type semiconductors, magnetic semiconductors, conductivity control, varistor applications, piezoelectric body applications, electroluminescent elements, and transparent TFTs.
  • a ZnO single crystal is used as a seed crystal substrate that is a growth substrate.
  • Any ZnO-based mixed crystal growth substrate can be used as long as it has a crystal structure similar to that of ZnO and does not react with the growth thin film. Examples thereof include sapphire, LiGaO 2 , LiAlO 2 , LiNbO 3 , LiTaO 3 , ScAlMgO 4 , GaN, and ZnO.
  • the target single crystal in the present invention is a ZnO-based mixed crystal single crystal
  • homoepitaxial growth using a ZnO substrate having a high degree of lattice matching between the substrate and the grown crystal can reduce crystallinity, distortion, and growth film. This is preferable in terms of reducing warpage and reducing the amount of impurity diffusion from the substrate.
  • the growth orientation of the Mg-containing ZnO mixed single crystal is the + c plane.
  • an Mg-containing ZnO mixed single crystal is grown on a seed crystal substrate, and then the substrate used for the growth can be removed by polishing or etching. At that time, by removing at least 10 ⁇ m, preferably 20 ⁇ m or more, on the ⁇ c plane side close to the growth substrate, it becomes possible to remove the heterogeneous layer of Zn and Mg and the Li diffusion layer from the substrate side.
  • any method of polishing or etching can be adopted, but grinding + polishing which allows easy film thickness management is preferable.
  • An Mg-containing ZnO mixed single crystal may be grown on the hydrothermal synthesis substrate.
  • a film thickness of about 100 ⁇ m is required at the growth stage.
  • the substrate side is fixed to the ceramic plate by WAX, and the liquid phase epitaxial growth surface can be flattened by a grinder. It is possible to polish by lapping and polishing at least one of the front and back surfaces by replacing the LPE surface side (+ c surface) with a ceramic plate and grinding and removing the substrate thickness with a grinder to make only the liquid phase epitaxial growth film. it can.
  • it is possible to remove the Li diffusion layer from the hydrothermal synthesis substrate by polishing the hydrothermal synthesis substrate side of the LPE growth film preferably at 10 ⁇ m, more preferably 20 ⁇ m or more.
  • an Mg-containing ZnO mixed crystal single crystal is grown by the above-described method for producing an Mg-containing ZnO mixed crystal single crystal, and this is used as a substrate.
  • a method for producing a Mg-containing ZnO mixed crystal single crystal laminate comprising growing a ZnO-based mixed crystal single crystal.
  • the band gap between the first growth layer and the second growth layer can be set arbitrarily, but considering the application of electronic elements and optical elements, the band gap of the first growth layer is preferably less than the band gap of the second growth layer.
  • LPE growth may be performed twice. For example, a plurality of melts having different compositions may be prepared in a growth furnace, and the laminate may be grown by moving the growth axis. . Alternatively, the laminate can be grown using a sliding boat method.
  • liquid phase epitaxial method As the self-standing Mg-containing ZnO mixed single crystal growth method in the present invention, a liquid phase epitaxial method (LPE method) is used. According to the liquid phase epitaxial method, it is easy to form a layer structure classified by function, which is particularly advantageous for application to electronic elements and optical elements.
  • the control of the liquid phase growth temperature is performed so that the solubility of ZnO and MgO and the amount of solvent evaporation, preferably the amount of evaporation of PbO and Bi 2 O 3 or the amount of evaporation of PbF 2 and PbO do not change significantly.
  • one or more third components can be added to the solvent.
  • Bi 2 O 3 may be added as a third component to the PbO and PbF 2 solvents.
  • an Mg-containing ZnO mixed single crystal having electrical conductivity is added to the liquid phase by containing one or more selected from the group consisting of Al, Ga, In, H and F. It can be manufactured by an epitaxial growth method.
  • the fifth embodiment of the present invention is a self-supporting Mg-containing ZnO mixed crystal single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed crystal single crystal described in the fourth embodiment, and is 50 ⁇ m or more. And has a uniform chemical composition of Zn and Mg in both the film thickness direction and the in-plane direction, and at least one of the front and back surfaces can be used as a substrate for epitaxial growth. It is a self-supporting Mg-containing ZnO mixed crystal single crystal wafer characterized by having A thickness of less than 50 ⁇ m is not preferable because it becomes difficult to handle. The upper limit of the thickness is not specified, but if it exceeds 500 ⁇ m, the growth time becomes longer.
  • the composition uniformity in the film thickness direction and in-plane direction of the self-supporting Mg-containing ZnO mixed single crystal wafer is preferably within ⁇ 10%, more preferably within ⁇ 5%.
  • the method for evaluating composition uniformity is as described above. If the composition uniformity exceeds ⁇ 10%, the transmittance in the near ultraviolet region decreases, which is not preferable.
  • the flatness of at least one of the front and back surfaces of the free-standing Mg-containing ZnO mixed crystal single crystal wafer may be such that epitaxial growth is possible.
  • the 50 ⁇ m square Ra at an arbitrary position of the free-standing Mg-containing ZnO-based mixed crystal single crystal wafer is preferably 0.5 nm or less, and more preferably 0.3 nm or less.
  • the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable.
  • the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping.
  • a preferred embodiment of the present invention is a self-standing Mg-containing ZnO mixed single crystal wafer having a band gap (Eg) value that is uniform in the in-plane direction and the thickness direction of the wafer and exceeds 3.30 eV. is there.
  • the uniformity of the band gap (Eg) value can be obtained from the PL and CL emission wavelengths as described above. If the band gap of the ZnO-based mixed crystal single crystal is less than 3.30 eV, the mixed crystal ratio of MgO is lowered.
  • the self-supporting Mg-containing ZnO mixed crystal single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment includes Al, Ga, In, H and 1 or more selected from the group consisting of F.
  • the substrate used for growth is removed by polishing, etching, or the like, electrodes can be formed on the front and back surfaces of the electronic element or optical element. Accordingly, it is possible to provide a Mg-containing ZnO mixed single crystal having self-supporting conductivity.
  • the self-supporting Mg-containing ZnO mixed single crystal having conductivity is transparent to LED light in a ZnO-LED device, and can be a lattice-matched substrate having conductivity.
  • the self-standing Mg-containing ZnO mixed single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment has an Li concentration in the plane of the wafer. direction, and a uniform relative thickness direction, and preferably 1 ⁇ 10 15 atoms / cm 3 or less, further preferably 1 ⁇ 10 14 atoms / cm 3 or less.
  • the Li concentration is uniform at 1 ⁇ 10 15 pieces / cm 3 or less
  • the Li concentration that destabilizes the device operation is 1 ⁇ 10 15 pieces / cm 3 or less in the entire self-supporting film. means.
  • the uniformity of the Li concentration can be evaluated by the method described above.
  • FIG. 1 A configuration diagram of the furnace used here is shown in FIG.
  • a platinum crucible 4 for melting a raw material and storing it as a melt is provided on a crucible base 9. Outside the platinum crucible 4 and on the side thereof, three-stage side heaters (upper heater 1, central heater 2, lower heater 3) for heating and melting the raw material in the platinum crucible 4 are provided. . The outputs of the heaters are controlled independently, and the heating amount for the melt is adjusted independently.
  • a core tube 11 is provided between the heater and the inner wall of the manufacturing furnace, and a furnace lid 12 for opening and closing the inside of the furnace is provided above the core tube 11.
  • a pulling mechanism is provided above the platinum crucible 4.
  • a pulling-up shaft 5 is fixed to the pulling mechanism, and a substrate holder 6 and a substrate 7 fixed by the holder are provided at the tip thereof.
  • a mechanism for rotating the pull-up shaft 5 is provided on the pull-up shaft 5.
  • a thermocouple 10 for managing the temperature of the crucible is provided below the platinum crucible 4.
  • the non-Al system is suitable for the members constituting the growth furnace.
  • a ZnO furnace material is optimal, but considering that it is not commercially available, MgO is suitable as a material that does not function as a carrier even when mixed in a ZnO thin film.
  • a quartz furnace material is also preferable.
  • calcium, silica, ZrO 2 and zircon (ZrO 2 + SiO 2 ), SiC, Si 3 N 4 and the like can be used.
  • the temperature of the production furnace is increased until the raw material is melted.
  • the temperature is raised to 800 to 1100 ° C. and left for 2 to 3 hours to stabilize the raw material melt.
  • the standing time may be shortened by stirring with a Pt stirring blade.
  • an offset is applied to the three-stage heater, and the bottom of the crucible is adjusted to be several degrees higher than the melt surface.
  • ⁇ H3 offset ⁇ 50 ° C After the bottom temperature of the crucible is adjusted to a seeding temperature of 700 to 950 ° C and the melt temperature is stabilized, the substrate is brought to the melt surface by lowering the pulling shaft while rotating the substrate at 5 to 120 rpm. Wetted in contact with. After allowing the substrate to adjust to the melt, the temperature starts to decrease at a constant temperature or from 0.01 to 3.0 ° C./hr, and the target ZnO single crystal or Mg-containing ZnO mixed single crystal is formed on the substrate surface. Grow. Even during growth, the substrate is rotated at 5 to 300 rpm by the rotation of the pulling shaft, and is rotated reversely at regular time intervals.
  • the substrate After crystal growth for about 30 minutes to 100 hours, the substrate is separated from the melt, and the melt component is separated by rotating the pulling shaft at a high speed of about 200 to 300 rpm. Thereafter, the target ZnO single crystal or Mg-containing ZnO mixed single crystal is obtained by cooling to room temperature over 1 to 24 hours.
  • Example 1 A ZnO single crystal was produced by a liquid phase epitaxial growth method through the following steps.
  • a platinum crucible having an inner diameter of 75 mm ⁇ , a height of 75 mmh, and a thickness of 1 mm was charged with 33.20 g, 829.53 g, and 794.75 g of ZnO, PbO, and Bi 2 O 3 as raw materials, respectively.
  • the concentration of ZnO as a solute is 7 mol%
  • the crucible charged with the raw material was placed in the furnace shown in FIG.
  • the pulling axis was continuously pulled up by about 500 ⁇ m.
  • the shaft pulling speed at this time is about 6.3 ⁇ m / hr.
  • the shaft rotation direction was reversed every two minutes.
  • the pulling-up shaft was raised to separate it from the melt, and the shaft was rotated at 100 rpm to shake off the melt components and then gradually cooled to room temperature to obtain a colorless and transparent ZnO single crystal.
  • the grown film was taken out from the LPE furnace and observed around the Pt jig, but no flux deposition was observed.
  • the LPE growth film thickness was 391 ⁇ m, and the growth rate at this time was about 4.9 ⁇ m / hr.
  • the back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX. About 50 ⁇ m was ground so that the + c plane LPE surface was flattened by a horizontal surface grinder. Then, the self-supporting ZnO single crystal was obtained by reversing the front and back and grinding the amount corresponding to the thickness of the hydrothermal synthetic substrate. The thickness was about 341 ⁇ m.
  • the self-supporting film was fixed to the ceramic plate again by WAX, lapped with diamond slurry, and polished with colloidal silica.
  • the polishing amount of the front and back surfaces of the free-standing film was 33 ⁇ m on the + c surface and 28 ⁇ m on the ⁇ c surface, and as a result, a free-standing ZnO single crystal having a thickness of about 280 ⁇ m was obtained. There were no cracks in the grinding and polishing process.
  • the ⁇ c plane was analyzed by dynamic SIMS to determine the Li concentration. The Li concentration was 5 ⁇ 10 13 pieces / cm 3 or less, which is the lower limit of detection, on both the ⁇ c planes.
  • the dynamic SIMS analysis is performed under the conditions of primary ion species; O 2+ , primary ion acceleration voltage; 8 KeV, measurement temperature; Further, the film was cut in a direction perpendicular to the c-plane, and the cut surface was subjected to SIMS analysis.
  • the Li concentration was 5 ⁇ 10 13 pieces / cm 3 below the detection lower limit.
  • the rocking curve half-value width of the (002) plane showing the crystallinity of the free-standing film is about 33 arcsec, indicating that the crystallinity is high.
  • the carrier concentration exhibiting conductivity was 2.0 ⁇ 10 17 particles / cm 3 and the carrier mobility was 165 cm 2 / V ⁇ sec. It shows that the quality is high also from the high carrier mobility.
  • AFM atomic force microscope
  • Example 2-10 and Comparative Example 1 A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that Ga 2 O 3 was charged into a Pt crucible.
  • continuous shaft pulling was changed to intermittent shaft pulling. That is, the process of stopping the shaft and raising 100 ⁇ m after 16 hours was repeated 5 times, and the total was raised by 500 ⁇ m in 80 hours.
  • the charge composition is shown in Table 1.
  • Table 2 shows the physical properties of the obtained free-standing film.
  • the carrier concentration increased and the carrier concentration of the self-supporting film of Example 9 charged with 2100 ppm with respect to ZnO was 1.0 ⁇ 10 19 atoms / cm 3 .
  • the carrier concentration can be controlled from 2.0 ⁇ 10 17 atoms / cm 3 to 1.0 ⁇ 10 19 atoms / cm 3 by charging Ga 2 O 3 .
  • the carrier mobility was 154 cm 2 / V ⁇ sec in Example 1 in which Ga 2 O 3 was not charged, and 64 cm 2 / V ⁇ sec in Example 9 in which 2100 ppm was charged. This seems to be a result of doping Ga, which is a foreign material.
  • the rocking curve half width of the (002) plane showing crystallinity is 23 to 71 arcsec between 0 to 2100 ppm of Ga 2 O 3 , indicating that the crystallinity is extremely high.
  • the ⁇ c surface portion which is the growth surface on the hydrothermal synthesis substrate side is polished and removed by 12-29 ⁇ m.
  • the Li concentration is 5 ⁇ 10 5 which is the SIMS detection lower limit for both ⁇ c surfaces. It was 13 pieces / cm 3 or less.
  • the carrier concentration of the free-standing ZnO single crystal wafer can be controlled from about 2.7 ⁇ 10 17 pieces / cm 3 to about 1 ⁇ 10 19 pieces / cm 3 by controlling the amount of Ga 2 O 3 charged.
  • an optical element or an electronic element is configured using a self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
  • Example 11-18 and Comparative Example 2 A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that Al 2 O 3 was charged into a Pt crucible and the charging composition shown in Table 3 was used. In Example 18, continuous shaft pulling was changed to intermittent shaft pulling. That is, the process of stopping the shaft and raising 100 ⁇ m after 16 hours was repeated 5 times, and the total was raised by 500 ⁇ m in 80 hours. Table 4 shows the physical properties of the obtained self-supporting film. As the Al 2 O 3 charge increased, the carrier concentration increased and the carrier concentration of the self-supporting film of Example 17 charged with 2200 ppm with respect to ZnO was 1.0 ⁇ 10 19 particles / cm 3 .
  • the carrier concentration can be controlled from 2.0 ⁇ 10 17 pieces / cm 3 to 1.2 ⁇ 10 19 pieces / cm 3 by charging Al 2 O 3 .
  • the carrier mobility was the Al 2 O 3 in Example 11 without charged to 163cm 2 / V ⁇ sec
  • the Al 2 O 3 Example 15 was charged 2200ppm of 95cm 2 / V ⁇ sec. This is considered to be a result of doping Al as a foreign material.
  • the rocking curve half width of the (002) plane showing crystallinity is 19 to 52 arcsec between 0 to 2179 ppm of Al 2 O 3 , indicating that the crystallinity is extremely high.
  • the ⁇ c surface portion which is the growth surface on the hydrothermal synthesis substrate side, is polished and removed by 13-24 ⁇ m. It became 13 pieces / cm 3 or less.
  • the carrier concentration of the free-standing ZnO single crystal wafer can be controlled from 2.0 ⁇ 10 17 pieces / cm 3 to about 1 ⁇ 10 19 pieces / cm 3 by controlling the amount of Al 2 O 3 charged.
  • an optical element or an electronic element is configured using a self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
  • Examples 19-22 A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that In 2 O 3 was charged into a Pt crucible and the charging composition shown in Table 5 was adopted. Table 6 shows the physical properties of the obtained self-supporting film. As the amount of In 2 O 3 charged increased, the carrier concentration increased and the carrier concentration of the self-supporting film of Example 22 charged with 140 ppm with respect to ZnO was 3.5 ⁇ 10 17 particles / cm 3 . From these results, it is shown that the carrier concentration can be controlled from 2.0 ⁇ 10 17 pieces / cm 3 to 3.5 ⁇ 10 17 pieces / cm 3 by charging In 2 O 3 .
  • the carrier mobility was 168 cm 2 / V ⁇ sec in Example 19 in which In 2 O 3 was not charged, and 134 cm 2 / V ⁇ sec in Example 22 in which 140 ppm was charged. This is considered to be a result of doping In which is a foreign substance.
  • the rocking curve half width of the (002) plane showing crystallinity is 19 to 58 arcsec between 0 to 140 ppm of In 2 O 3 , indicating that the crystallinity is extremely high.
  • the ⁇ c surface portion which is the growth surface on the hydrothermal synthesis substrate side, was polished and removed by 19-24 ⁇ m. It became 13 pieces / cm 3 or less.
  • the carrier concentration of the freestanding ZnO single crystal wafer can be controlled from 2.0 ⁇ 10 17 pieces / cm 3 to about 3.5 ⁇ 10 17 pieces / cm 3 by controlling the amount of In 2 O 3 charged.
  • an optical element or an electronic element is configured using the self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
  • the bottom temperature of the crucible was maintained at about 940 ° C. for 1 hour, and the mixture was stirred and dissolved with a Pt stirring jig. After that, the temperature is lowered until the bottom temperature of the crucible reaches about 835 ° C., and a ZnO single crystal substrate having a size of 10 mm ⁇ 10 mm ⁇ 529 ⁇ mt grown in a hydrothermal synthesis method and having a size of 10 mm ⁇ 10 mm ⁇ 529 ⁇ mt is contacted as a seed crystal.
  • the shaft was grown at the same temperature for 80 hours while rotating the shaft at 30 rpm.
  • the set temperatures of H1, H2, and H3 were decreased at a rate of ⁇ 0.1 ° C./hr while maintaining the offset difference. Further, during the LPE growth, that is, over 80 hours, the pulling axis was continuously pulled up by about 500 ⁇ m. The shaft pulling speed at this time is about 6.3 ⁇ m / hr. At this time, the shaft rotation direction was reversed every two minutes. Thereafter, the pulling-up shaft was raised to separate it from the melt, and the shaft was rotated at 100 rpm to shake off the melt components and then gradually cooled to room temperature to obtain a colorless and transparent ZnO single crystal. After cooling to room temperature, the grown film was taken out from the LPE furnace and observed around the Pt jig, but no flux deposition was observed.
  • the LPE growth thickness was 343 ⁇ m, and the growth rate at this time was about 4.3 ⁇ m / hr. Subsequently, the following independence treatment was performed.
  • the back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX. About 50 ⁇ m was ground so that the + c plane LPE surface was flattened by a horizontal surface grinder. Then, the self-supporting ZnO single crystal was obtained by reversing the front and back and grinding the amount corresponding to the thickness of the hydrothermal synthetic substrate. The thickness was about 251 ⁇ m.
  • the self-supporting film was fixed to the ceramic plate again by WAX, lapped with diamond slurry, and polished with colloidal silica.
  • the polishing amount of the front and back surfaces of the free-standing film was 24 ⁇ m on the + c plane and 18 ⁇ m on the ⁇ c plane, and as a result, a free-standing ZnO single crystal having a thickness of about 251 ⁇ m was obtained. There were no cracks in the grinding and polishing process.
  • the ⁇ c plane was analyzed by SIMS to determine the Li concentration. The Li concentration was 5 ⁇ 10 13 pieces / cm 3 or less, which is the lower limit of detection, on both the ⁇ c planes.
  • the rocking curve half-value width of the (002) plane showing the crystallinity of the free-standing film is about 31 arcsec, indicating that the crystallinity is high.
  • the carrier concentration showing conductivity was 1.0 ⁇ 10 19 atoms / cm 3 , and the carrier mobility was 60 cm 2 / V ⁇ sec. It shows that the quality is high also from the high carrier mobility.
  • Ra 0.3 nm.
  • Example 24 was performed in the same manner as in Example 9 except that the continuous shaft pulling rate was 2.0 ⁇ m / hr.
  • Example 25 was performed in the same manner as Example 9 except that the continuous shaft pulling rate was 50.0 ⁇ m / hr.
  • a self-supporting film could be produced without generation of cracks.
  • the lattice constant and the band gap were almost the same as those in Example 9, but in Example 24 where the growth rate was low, the rocking curve half of the (002) plane was used. The value range narrowed and the crystallinity improved.
  • Example 25 where the growth rate was high, the full width at half maximum of the rocking curve on the (002) plane was widened, and a decrease in crystallinity was observed.
  • Example 26 An Mg-containing ZnO-based mixed crystal single crystal was produced by a liquid phase epitaxial (LPE) growth method through the following steps.
  • LPE liquid phase epitaxial
  • the concentration of ZnO as a solute at this time is 7 mol%
  • the temperature is lowered until the bottom temperature of the crucible reaches about 808 ° C., and a ZnO single crystal substrate having a size of 10 mm ⁇ 10 mm ⁇ 538 ⁇ mt grown in a hydrothermal synthesis method and having a size of 10 mm ⁇ 10 mm ⁇ 538 ⁇ mt is brought into contact with the seed crystal as a seed crystal.
  • the shaft was grown at the same temperature for 80 hours while rotating the shaft at 30 rpm.
  • the set temperatures of H1, H2, and H3 were decreased at a rate of ⁇ 0.1 ° C./hr while maintaining the offset difference. Further, during the LPE growth, that is, over 80 hours, the pulling axis was continuously pulled up by about 500 ⁇ m.
  • the shaft pulling speed at this time is about 6.3 ⁇ m / hr.
  • the shaft rotation direction was reversed every two minutes. Thereafter, the pulling-up shaft is raised to separate it from the melt, and the shaft is rotated at 100 rpm to shake off the melt components, and then slowly cooled to room temperature to form a colorless and transparent Mg-containing ZnO-based mixed crystal single crystal. Obtained crack-free.
  • the LPE growth film thickness was 397 ⁇ m, and the growth rate at this time was about 5.0 ⁇ m / hr. Subsequently, the following independence treatment was performed. The back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX.
  • the Mg-containing ZnO mixed crystal single crystal when the Mg / (Zn + Mg) composition varies by 10% ⁇ 1% (corresponding to ⁇ 10% in composition change), the PL emission wavelength is about 357.5 nm ⁇ 2.1 nm, and the band gap is Since it changes by about 3.468 eV ⁇ 0.20 eV, the Mg / (Zn + Mg) uniformity of the self-supporting film in Example 26 is about ⁇ 1%, and similarly the band gap uniformity is about ⁇ 0.6%.
  • Li concentration was measured using dynamic SIMS on the front and back surfaces of the self-supporting film and the surface cut perpendicular to the c-plane, the Li concentration was 5 ⁇ 10 13 pieces / cm which is the lower limit of detection on any surface. 3 or less.
  • Table 10 shows LPE growth conditions, grinding and polishing film thickness, and physical properties in Example 26.
  • the “carrier concentration” and “carrier mobility” were measured at room temperature by the Van Der Pauw method using a Hall effect / specific resistance measuring device manufactured by Toyo Technica.
  • Examples 27-31 A self-supporting film was obtained by the method shown in Table 11 while changing the MgO preparation composition and the shaft pulling method of Example 26.
  • the band gap obtained from the PL emission wavelength is 3.32 to 3.54 eV
  • the film is a self-supporting Mg-containing ZnO mixed single crystal wafer having a wider band gap than the hydrothermal synthetic substrate. Is shown.
  • the (002) plane rocking curve half-width is 27-45 arcsec and has high crystallinity.
  • the Li concentrations on the front and back surfaces after the self-supporting treatment were all 5 ⁇ 10 13 pieces / cm 3 or less, which were below the detection lower limit.
  • Example 31 the shaft pulling method was changed from continuous to intermittent.
  • the step of lifting the shaft by 100 ⁇ m was repeated 5 times, and the shaft was pulled by a total of 500 ⁇ m in 80 hours.
  • the pulling average speed is 6.3 ⁇ m / hr, which is the same as the pulling speed of Example 30.
  • the crystallinity of Example 31 is lower. The intermittent pulling seems to reflect the instability of crystal growth when the shaft is pulled up.
  • Comparative Example 3-7 A self-supporting Mg-containing ZnO mixed single crystal wafer film was produced in the same manner as in Examples 27-31 except that the shaft was not pulled up. In any growth film, flux precipitation based on the Pt jig was observed, and cracks occurred during any of the growth, cooling, and grinding / polishing steps. From the above results, when performing thick film growth to obtain a self-supporting Mg-containing ZnO mixed crystal single crystal wafer, it is possible to suppress flux precipitation based on the Pt jig by performing axial pulling growth. I understand that When the flux precipitation is suppressed, it is possible to reduce the generation of cracks in the growth, cooling and grinding / polishing steps.
  • Example 32 was performed in the same manner as in Example 31 except that the intermittent shaft pulling was changed to continuous shaft pulling and the continuous shaft pulling speed was changed to 2.0 ⁇ m / hr. . In Example 31, except that the intermittent axial pulling was changed to continuous axial pulling, the continuous axial pulling speed was changed to 50.0 ⁇ m / hr, and the growth time was changed from 80 hours to 40 hours.
  • Example 33 was carried out in the same manner as above. In Examples 32 and 33, a self-supporting film could be produced without generation of cracks.
  • Example 32 In the physical properties of the self-supporting films obtained in Examples 32 and 33, the lattice constant and the band gap were almost the same as in Example 31, but in Example 32 where the growth rate was low, the (002) plane rocking curve half The value range narrowed and the crystallinity improved. On the other hand, in Example 33 having a high growth rate, the rocking curve half-value width of the (002) plane was widened, and the crystallinity was lowered.
  • the present invention relates to a ZnO-based semiconductor material, and can be used particularly in the fields of optics and electric / electronic industries.

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Abstract

ZnO as a solute is mixed with a solvent, and the solute is melted. A seed-crystal substrate is brought into direct contact with the resultant melt, and the seed-crystal substrate is continuously or intermittently pulled up, whereby a ZnO single crystal can be grown on the seed-crystal substrate by liquid phase epitaxy. ZnO and MgO as solutes are mixed with a solvent, and the solutes are melted. A seed-crystal substrate is brought into direct contact with the resultant melt, and the seed-crystal substrate is continuously or intermittently pulled up to thereby grow an Mg-containing ZnO mixed single crystal by liquid phase epitaxy. Thereafter, the substrate is removed by abrasion or etching, and one c-plane side of the single crystal, said side having been grown by liquid phase epitaxy, is abraided or etched. Thus, the self-supporting wafer of an Mg-containing ZnO mixed single crystal can be obtained.

Description

ＺｎＯ単結晶の製造方法、それによって得られた自立ＺｎＯ単結晶ウエファー、並びに自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーおよびそれに用いるＭｇ含有ＺｎＯ系混晶単結晶の製造方法Manufacturing method of ZnO single crystal, free-standing ZnO single crystal wafer obtained thereby, free-standing Mg-containing ZnO mixed crystal single crystal wafer, and manufacturing method of Mg-containing ZnO mixed single crystal used therefor
　本発明は、ＺｎＯ系半導体材料に関し、特に、光学分野、電気・電子工業分野において有用なＺｎＯ単結晶の製造方法とそれによって得られた自立ＺｎＯ単結晶ウエファーに関する。更に、本発明は、特に、光学分野、電気・電子工業分野において有用な組成均一性が高い自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーとそれに用いるＭｇ含有ＺｎＯ系混晶単結晶の製造方法に関する。 The present invention relates to a ZnO-based semiconductor material, and more particularly to a method for producing a ZnO single crystal useful in the fields of optics and electric / electronic industry and a free-standing ZnO single crystal wafer obtained thereby. Furthermore, the present invention relates to a self-supporting Mg-containing ZnO mixed crystal single crystal wafer having high composition uniformity that is particularly useful in the fields of optics and electric / electronic industries, and a method for producing an Mg-containing ZnO mixed crystal single crystal used therefor.

　従来より、様々な機能を有する光・電子デバイスには、Ｓｉ、ＧａＡｓおよびＧａＮ等が用いられてきた。最近では、ＧａＮを用いた発光デバイスや電子デバイス開発が活発に行われている。一方、酸化物に着目すると、ＺｎＯは、バリスタ、ガスセンサー、日焼け止め等に用いられてきたが、最近その光学特性、電子素子特性および圧電特性から光学素子、電子素子、圧電素子および透明電極等への応用が図られ、注目を集めている。特に、ＺｎＯがＧａＮと同様に直接遷移型の３．３～３．４ｅＶのバンドギャップを有し、３８０ｎｍの紫外光を出すことが知られており、青色から紫外域に至る短波長の光を発光する発光素子用半導体に対する用途および応用に対する研究開発が盛んとなっている。
Conventionally, Si, GaAs, GaN, and the like have been used for optical and electronic devices having various functions. Recently, light-emitting devices and electronic devices using GaN have been actively developed. On the other hand, focusing on oxides, ZnO has been used for varistors, gas sensors, sunscreens, etc. Recently, optical elements, electronic elements, piezoelectric elements, transparent electrodes, etc., due to its optical characteristics, electronic element characteristics and piezoelectric characteristics. Has been attracting attention. In particular, it is known that ZnO has a direct transition type band gap of 3.3 to 3.4 eV like GaN, and emits 380 nm ultraviolet light, and emits light of a short wavelength from blue to ultraviolet region. Research and development for applications and applications for semiconductors for light-emitting elements that emit light has become active.

　また、ＺｎＯ系半導体単結晶積層体において、電界効果トランジスタとは異なり、電界を印加しない状態で半導体同士を接触させて電荷分離を生じさせる方法のひとつとして変調ドーピング法がある。例えば、特開２００５－７２０６７号公報（特許文献１）は、バンドギャップが広く電子濃度の高い半導体とバンドギャップが狭く電子移動度の高い半導体とを積層することにより、電子濃度の高い半導体から電子移動度の高い半導体への電荷移動が誘起され、高い移動度をもった層を電子が移動することによって高い電子濃度と高電子移動度を共に満足する半導体材料を開示している。
In addition, unlike a field effect transistor in a ZnO-based semiconductor single crystal stacked body, there is a modulation doping method as one method for causing charge separation by bringing semiconductors into contact with each other without applying an electric field. For example, Japanese Patent Laying-Open No. 2005-72067 (Patent Document 1) discloses that a semiconductor having a high band density and a semiconductor having a high band density and a semiconductor having a low band gap and a high electron mobility are stacked to form an electron from a semiconductor having a high band density. A semiconductor material that satisfies both a high electron concentration and a high electron mobility is disclosed by inducing charge transfer to a semiconductor with high mobility and moving electrons through a layer with high mobility.

　更に、ＺｎＯを用いた紫外線発光デバイスを製造するために、広いバンドギャップを持つＩＩ－ＶＩ族半導体混晶のＺｎ１－ｘＭｇｘＯがパルスレーザー堆積法により成長温度６００℃で得られ、組成ｘを調整することでＺｎＯより広いバンドギャップが得られることが示されている（A.Ohtomo et.al , Applied Physics Letters , Vol.72 , No.19 , 11 May 1998 , 2466-2468）（非特許文献１）。また、発光素子への応用を考慮した場合、発光効率を上げるためには、ダブルへテロ構造を採用する必要がある。上記構造を採用することにより、キャリヤの閉じ込めや光取り出し効率が向上し、発光効率が向上する。上記構造を形成するためには、発光層をバンドギャップが高いｎ層とｐ層で挟み込む必要があり、そのためには、ＺｎＯよりバンドギャップが高いＺｎＯ系混晶単結晶が必要となり、同時にｎ型およびｐ型のＺｎＯ単結晶が必要となる。
Furthermore, in order to manufacture an ultraviolet light emitting device using ZnO, a II-VI group semiconductor mixed crystal Zn 1-x Mg x O having a wide band gap is obtained by a pulse laser deposition method at a growth temperature of 600 ° C. It has been shown that a wider band gap than ZnO can be obtained by adjusting x (A. Ohtomo et.al, Applied Physics Letters, Vol.72, No.19, 11 May 1998, 2466-2468) Patent Document 1). In consideration of application to a light emitting element, it is necessary to adopt a double hetero structure in order to increase the light emission efficiency. By employing the above structure, carrier confinement and light extraction efficiency are improved, and light emission efficiency is improved. In order to form the above structure, it is necessary to sandwich the light emitting layer between an n-layer and a p-layer having a high band gap. For this purpose, a ZnO-based mixed crystal single crystal having a higher band gap than ZnO is required, and at the same time an n-type In addition, a p-type ZnO single crystal is required.

　ＺｎＯ系半導体単結晶の電子素子特性や光学素子特性を発揮させるためには、高い結晶性が必要となる。ＺｎＯ系半導体単結晶は、従来、ＺｎＯ、ＳｃＡｌＭｇＯ４およびサファイヤ等の絶縁性基板を用いた気相成長法で成長させていた。高い結晶性を実現するためには、格子不整合が少ない基板を用いる必要がある。そのためには、ＺｎＯ単結晶を基板として使用することが望ましい。しかしながら、市販のＺｎＯ単結晶基板は、水熱合成法で成長されており、鉱化剤として用いられるＬｉＯＨに基づくＬｉのＺｎＯ単結晶への混入が避けられない。ＺｎＯ中のＬｉは拡散しやすく、デバイス稼動時にＬｉが移動してデバイス動作を不安定にする問題点があり、ＺｎＯ基板中のＬｉは少なければ少ないほど良い。そこで、ポストグロースアニールで、水熱合成基板内のＬｉ濃度を低減させる手法が特開２００７－２０４３２４号公報（特許文献２）に開示されている。同公報によれば、１１００℃で１～２時間のアニールで８．４×１０１６個／ｃｍ３から２．０×１０１７個／ｃｍ３程度、１３００℃で２時間程度アニール処理すると９×１０１４個／ｃｍ３程度までＺｎＯ中のＬｉ濃度を低減できると記載されている。同公報によればアニール処理することでＬｉ濃度を低減させることは可能である。しかし、この方法ではアニール工程が必要になるため工程が煩雑になり、またアニール処理を施してもＬｉが１×１０１５個／ｃｍ３程度残存するという問題点があった。
High crystallinity is required to exhibit the electronic element characteristics and optical element characteristics of the ZnO-based semiconductor single crystal. Conventionally, a ZnO-based semiconductor single crystal has been grown by a vapor phase growth method using an insulating substrate such as ZnO, ScAlMgO 4 and sapphire. In order to achieve high crystallinity, it is necessary to use a substrate with less lattice mismatch. For that purpose, it is desirable to use a ZnO single crystal as a substrate. However, a commercially available ZnO single crystal substrate is grown by a hydrothermal synthesis method, and it is inevitable that Li based on LiOH used as a mineralizer is mixed into the ZnO single crystal. Li in ZnO is easily diffused, and there is a problem that Li moves when the device is operated to make the device operation unstable. The smaller the Li in the ZnO substrate, the better. Therefore, a technique for reducing the Li concentration in the hydrothermal synthesis substrate by post-growth annealing is disclosed in Japanese Patent Laid-Open No. 2007-204324 (Patent Document 2). According to the publication, annealing at 1100 ° C. for 1 to 2 hours is about 8.4 × 10 16 pieces / cm 3 to 2.0 × 10 17 pieces / cm 3 , and annealing at 1300 ° C. for about 2 hours is 9 ×. It is described that the Li concentration in ZnO can be reduced to about 10 14 pieces / cm 3 . According to the publication, it is possible to reduce the Li concentration by annealing. However, this method requires an annealing process, which makes the process complicated, and there is a problem that about 1 × 10 15 pieces / cm 3 of Li remains even after annealing.

　一方、膜厚が厚いＺｎＯ系半導体単結晶を成長させ、その後水熱合成基板を研磨やエッチングで除去することにより該ＺｎＯ系半導体単結晶を自立化させることができれば、水熱合成基板からのＬｉ不純物の混入を著しく低減できる。更には、導電性を付与できる不純物を同時にドープし、自立化させることができれば、Ｌｉ濃度が低く導電性を有する自立導電性ＺｎＯ単結晶ウエファーを提供することが可能となる。
On the other hand, if the ZnO-based semiconductor single crystal can be made self-supporting by growing a thick ZnO-based semiconductor single crystal and then removing the hydrothermally-synthesized substrate by polishing or etching, Li Impurity contamination can be significantly reduced. Furthermore, if an impurity capable of imparting conductivity can be doped at the same time and become self-supporting, it is possible to provide a self-supporting conductive ZnO single crystal wafer having a low Li concentration and conductivity.

　本発明者らは、先に「液相成長法によるＺｎＯ単結晶の製造方法」（国際公開第２００７／１００１４６号パンフレット（特許文献３）を出願している。この公報に記載の発明を用いれば、膜厚が厚いＺｎＯ単結晶を成長可能である。しかしながら、この発明を用いた場合、クラックフリーで自立ＺｎＯ単結晶を製造する場合、歩留が低いことが判明した。本発明者らが鋭意研究したところ、基板をホールドするＰｔ冶工具近傍でのフラックス析出が歩留を低下させる要因であることが分かった。このように、本発明者らが出願した方法を用いれば、膜厚が厚いＺｎＯ単結晶を成長させ、成長に用いた基板を除去すれば、自立したＺｎＯ単結晶を製造することは可能であるが、成長に用いたＰｔ冶工具に析出するフラックス成分を基点としたクラックが成長、冷却および研削／研磨過程で発生するという問題点があった。
The present inventors have previously filed a “method for producing a ZnO single crystal by a liquid phase growth method” (International Publication No. 2007/100146 pamphlet (Patent Document 3). If the invention described in this publication is used, However, when this invention is used, it has been found that the yield is low when a free-standing ZnO single crystal is produced without cracks. As a result of research, it has been found that flux precipitation in the vicinity of the Pt jig holding the substrate is a factor that reduces the yield, and thus, if the method applied by the present inventors is used, the film thickness is large. It is possible to produce a self-supporting ZnO single crystal by growing the ZnO single crystal and removing the substrate used for the growth, but based on the flux component deposited on the Pt jig tool used for the growth. Rack growth, there is a problem that occurs in the cooling and grinding / polishing process.

本発明者らは、上記の問題点を鋭意検討し、以下の問題点があることを見出した。図１を用いて説明する。これまでの方法では、酸化亜鉛Ａ－１を基板として結晶層を液相エピタキシャル（Liquid phase epitaxial：ＬＰＥ）成長させるため（以下、成長した結晶層を「ＬＰＥ層」という場合がある。）、成長後は、水熱合成基板中のＬｉ濃度が減少したＢ－３部と元々のＬｉ濃度を有するＢ－１部となる。また、ＬＰＥ層Ｂ－２を成長させる際、初期に成長した部分では水熱合成基板中のＬｉが拡散し、ＬＰＥ成長膜中にＬｉ濃度が増加したＢ－４層が形成される。このため、Ｂ－１およびＢ－３を取り除くのみでは、得られた自立基板は、本来得るべきＬＰＥ層Ｂ－２とＬｉ拡散層Ｂ－４とから構成されるものであった。これを成長用基板として光学素子あるいは電子素子を形成すると、Ｂ－２に比べて、僅かにＬｉ濃度が高いＢ－４層が原因となり、デバイス特性を不安定化させていた。
　また、ＺｎＯ基板と成長する不純物ドープＺｎＯ膜とでは、少なからず格子不整合が発生するが、歪みの緩和の面でも厚膜成長が必要となる。しかしながら、気相成長では成長速度が低く、厚膜成長が極めて困難であった。一方、液相成長法では、過飽和度を制御することで成長速度を制御でき、比較的高い成長速度が可能となる。
The present inventors diligently studied the above problems and found that there are the following problems. This will be described with reference to FIG. In the conventional methods, the crystal layer is grown by liquid phase epitaxial (LPE) using zinc oxide A-1 as a substrate (hereinafter, the grown crystal layer may be referred to as “LPE layer”). After that, the B-3 part in which the Li concentration in the hydrothermal synthesis substrate is decreased and the B-1 part having the original Li concentration are obtained. Further, when the LPE layer B-2 is grown, Li in the hydrothermal synthesis substrate diffuses in the initially grown portion, and a B-4 layer having an increased Li concentration is formed in the LPE growth film. For this reason, only by removing B-1 and B-3, the obtained self-supporting substrate is composed of the LPE layer B-2 and the Li diffusion layer B-4 that should be originally obtained. When an optical element or an electronic element was formed using this as a growth substrate, the B-4 layer having a slightly higher Li concentration than B-2 caused the device characteristics to become unstable.
In addition, there is a considerable lattice mismatch between the ZnO substrate and the grown impurity-doped ZnO film, but thick film growth is also necessary in terms of strain relaxation. However, in vapor phase growth, the growth rate is low, and thick film growth is extremely difficult. On the other hand, in the liquid phase growth method, the growth rate can be controlled by controlling the degree of supersaturation, and a relatively high growth rate is possible.

　一方、前述したように、気相成長および液相成長においては、絶縁性材料を基板に用いることが多い。このため、ＺｎＯ系混晶単結晶を用いた電子素子や光学素子を形成するためには、同一方向に電極を形成すること等の工夫が必要であった。この方法では、電子素子や光学素子の作製工程が複雑となり、コスト高の要因となる上、ｎ型コンタクト層（ｎ＋）層の一部に電界が集中し素子寿命が短くなる、等の問題点があった。しかしながら、絶縁性基板を用いて電気伝導性を持ったＺｎＯ膜を厚く成長させ、不要となる絶縁性基板を研磨等で除去できれば、表裏に電極を形成でき、デバイスの作製工程においても、デバイス特性や寿命の面でも性能向上が期待できる（図２参照）。
On the other hand, as described above, an insulating material is often used for a substrate in vapor phase growth and liquid phase growth. For this reason, in order to form an electronic element or an optical element using a ZnO-based mixed crystal single crystal, it is necessary to devise such as forming electrodes in the same direction. In this method, the manufacturing process of the electronic element and the optical element is complicated, resulting in high cost, and the problem is that the electric field is concentrated on a part of the n-type contact layer (n + ) layer and the lifetime of the element is shortened. There was a point. However, if an insulating substrate is used to grow a thick ZnO film with electrical conductivity and the unnecessary insulating substrate can be removed by polishing, etc., electrodes can be formed on the front and back sides, and device characteristics can be obtained even in the device fabrication process. In addition, it can be expected to improve performance in terms of life (see Fig. 2).

　更に、上記材料の研究としてのＺｎＯ系半導体単結晶およびその積層体は非熱平衡成長である気相成長法により成長されており（例えば特開２００３－０４６０８１号公報（特許文献４））、非熱平衡成長欠陥の混入が避けられず、結晶品質が十分なものとはいえない。従来の半導体素子の一例である電界効果トランジスタやｐｎ接合発光素子などでは、その結晶性が光学特性や半導体特性に大きく関与する。前述したように気相成長法による結晶の結晶品質は十分なものではなかったため、本来の性能を十分発揮できないという問題点があった。そのため上記の用途などに適用および発展させていくためには、結晶品質の高いＺｎＯ単結晶の製造方法を確立させることが重要な課題となる。
Further, a ZnO-based semiconductor single crystal and a laminate thereof as a study of the above materials are grown by a vapor phase growth method that is non-thermal equilibrium growth (for example, Japanese Patent Application Laid-Open No. 2003-046081 (Patent Document 4)). Mixing of growth defects is unavoidable, and the crystal quality is not sufficient. In a field effect transistor, a pn junction light emitting element, or the like, which is an example of a conventional semiconductor element, the crystallinity is greatly involved in optical characteristics and semiconductor characteristics. As described above, since the crystal quality of the crystal by the vapor phase growth method is not sufficient, there is a problem that the original performance cannot be sufficiently exhibited. Therefore, in order to apply and develop the above-mentioned uses, it is an important issue to establish a manufacturing method of ZnO single crystal with high crystal quality.

　ＺｎＯ系半導体単結晶を成長させる方法としては、従来、スパッタ法、ＣＶＤ法およびＰＬＤ法等が用いられてきた。これらの方法では、ＺｎＯ系半導体層の成長方位は－ｃ面方位であった。－ｃ面成長では、アクセプターを取り込みにくいという問題点があった（Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77）（非特許文献２）。ＺｎＯ系半導体層の場合、ｎ型成長は比較的容易であるが、ｐ型成長が困難であることを考慮すると、－ｃ面成長では、よりｐ型層を成長することが困難となるという問題点があった。
Conventionally, sputtering, CVD, PLD, and the like have been used as methods for growing a ZnO-based semiconductor single crystal. In these methods, the growth orientation of the ZnO-based semiconductor layer was the −c plane orientation. In the -c plane growth, there is a problem that it is difficult to incorporate an acceptor (Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77) (Non-patent Document 2). In the case of a ZnO-based semiconductor layer, n-type growth is relatively easy, but considering that p-type growth is difficult, it is difficult to grow a p-type layer with -c plane growth. There was a point.

　また、本発明者らは、鋭意検討した結果、溶質および溶媒の組成を工夫することによりＭｇ含有ＺｎＯ系混晶単結晶を液相エピタキシャル（Liquid phase epitaxial：ＬＰＥ）成長法で厚膜成長させることに成功した。しかしながら、単に、混晶層を成長させた後に、基板を取り除くのみでは、得られた自立Ｍｇ含有ＺｎＯ混晶単結晶の表面と裏面とに、僅かなバンドギャップ差がみとめられ、想定した光透過率を得ることができなかった。
In addition, as a result of intensive studies, the inventors have devised the composition of the solute and the solvent to grow a Mg-containing ZnO mixed crystal single crystal by a liquid phase epitaxial (LPE) growth method. succeeded in. However, simply removing the substrate after growing the mixed crystal layer reveals a slight band gap difference between the front and back surfaces of the obtained self-supporting Mg-containing ZnO mixed single crystal, and the assumed light transmission The rate could not be obtained.

　本発明者らは、上記の問題点を鋭意検討し、以下の問題点があることを見出した。再度、図１を用いて説明する。これまでの方法では、酸化亜鉛Ａ－１を基板として混晶結晶をＬＰＥ成長させるため、成長後は、Ａ－１の水熱合成基板側にＭｇが拡散し、元々Ａ－１であったものが、純酸化亜鉛としての状態が保たれたＢ－１部分とＭｇが拡散してきたＢ－３部分という構成となる。また、混晶層Ｂ－２を成長させる際、初期に成長した部分からは、基板に対してＭｇが拡散し、基板側に拡散層Ｂ－３ができるのと同様に、混晶成長層側にもＭｇ濃度が低下した拡散層Ｂ－４が形成される。このため、Ｂ－１およびＢ－３を取り除くのみでは、自立Ｍｇ含有ＺｎＯ混晶単結晶は、本来得るべき混晶層Ｂ－２と拡散層Ｂ－４から構成されるものであった。これを近紫外線透明な基板として光学素子あるいは電子素子を形成すると、Ｂ－２に比べて、僅かにバンドギャップが狭められたＢ－４が原因となり、十分な光透過率が得られなかった。また、ＬＰＥ成長に用いる水熱合成基板には、前述したようにＬｉが不純物として含まれており、特に基板表面にはＬｉ不純物濃縮層が形成されていた。このため、Ｂ－４層にはＬｉの拡散層が形成されており、組成は不均一になっていた。
The present inventors diligently studied the above problems and found that there are the following problems. The description will be made again with reference to FIG. In the conventional method, since the mixed crystal is grown by LPE using zinc oxide A-1 as the substrate, after the growth, Mg diffuses to the hydrothermal synthesis substrate side of A-1 and was originally A-1. However, the structure is a B-1 portion in which the state as pure zinc oxide is maintained and a B-3 portion in which Mg is diffused. Further, when the mixed crystal layer B-2 is grown, Mg is diffused from the initially grown portion to the substrate, so that the diffusion layer B-3 is formed on the substrate side. In addition, a diffusion layer B-4 having a reduced Mg concentration is formed. Therefore, only by removing B-1 and B-3, the self-supporting Mg-containing ZnO mixed crystal single crystal is composed of the mixed crystal layer B-2 and the diffusion layer B-4 that should originally be obtained. When an optical element or an electronic element was formed using this as a near-ultraviolet transparent substrate, sufficient light transmittance could not be obtained due to B-4 having a slightly narrower band gap than B-2. Further, as described above, Li is contained as an impurity in the hydrothermal synthesis substrate used for LPE growth, and in particular, a Li impurity concentrated layer is formed on the substrate surface. Therefore, a Li diffusion layer was formed in the B-4 layer, and the composition was nonuniform.

　ところで、ＺｎＯ系ＬＥＤ成長用基板としては、成長させるＺｎＯと格子整合し、かつＬＥＤ光に対して透明な基板が光取出し効率の面でも最適となる。そのためには、Ｍｇ含有ＺｎＯ系混晶単結晶のみで構成され、かつＺｎＯよりバンドギャップが大きい自立Ｍｇ含有ＺｎＯ系混晶単結晶が好適となる。
By the way, as a ZnO-based LED growth substrate, a substrate that is lattice-matched with ZnO to be grown and is transparent to LED light is optimal in terms of light extraction efficiency. For this purpose, a self-supporting Mg-containing ZnO mixed crystal single crystal composed only of the Mg-containing ZnO mixed crystal single crystal and having a band gap larger than that of ZnO is suitable.

　ＺｎＯ系混晶単結晶およびその積層体を成長させる方法としては、従来、スパッタ法、ＣＶＤ法およびＰＬＤ法等が用いられてきた。これらの方法では、ＺｎＯ系半導体層の成長方位は－ｃ面方位であった。しかし、－ｃ面成長では、アクセプターを取り込みにくいという問題点があった（Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77）（非特許文献２）。ＺｎＯ系混晶層の場合、ｎ型成長は比較的容易であるが、ｐ型成長が困難であることを考慮すると、－ｃ面成長では、よりｐ型層を成長することが困難となる問題点があった。また、－ｃ面成長膜は酸素面であるため、酸によるエッチング速度が速く制御が困難である上、平坦性の高いエッチングが困難という問題点があった。
Conventionally, sputtering, CVD, PLD, and the like have been used as a method for growing a ZnO-based mixed crystal single crystal and a laminate thereof. In these methods, the growth orientation of the ZnO-based semiconductor layer was the −c plane orientation. However, in the -c plane growth, there is a problem that it is difficult to incorporate an acceptor (Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77) (Non-patent Document 2). In the case of a ZnO-based mixed crystal layer, n-type growth is relatively easy, but considering that p-type growth is difficult, it is difficult to grow a p-type layer with -c plane growth. There was a point. Further, since the -c plane growth film is an oxygen surface, there are problems that the etching rate with acid is fast and difficult to control, and that etching with high flatness is difficult.
　また、酸化物半導体を中心に、透明電子デバイスが検討されている。ｐ－Ｓｉは、バンドギャップが狭く、光照射によるフォトキャリアーの発生が、誤動作の原因となるため、ｐ－ＳｉからなるＴＦＴでは、光を遮断するための金属マスクが必要となる。したがって、ｐ－Ｓｉを用いたＴＦＴでは、光透過性が得られない。これに対して、可視光を吸収しない半導体を利用したＴＦＴは、光の影響を受けることなく正常な動作が期待される。現在、液晶パネル用ＴＦＴは、ｐ－Ｓｉからなっており、その金属マスクの存在から、光が透過出来る部分の割合は、５０％程度とされている。そのため、金属マスクが不要な透明ＴＦＴを得ることで、このエネルギー効率の改善が可能と考えられる。

　一方で、酸化亜鉛を用いたＴＦＴでは、吸収端の波長が僅かに可視光にかかるために、白色の再現性に劣るという報告や、多結晶酸化亜鉛では、移動度に劣るという意見もある。
　尚、Ｍｇ含有ＺｎＯ系混晶単結晶において、１０００℃程度までの高温で結晶成長を行った場合、熱力学的に得ることが可能な、安定なＭｇ／（Ｚｎ＋Ｍｇ）比ｘは、０＜ｘ＜０．１５であることが知られている（H.Ryoken et.al., Journal of Crystal Growth 287(2006)134-138）（非特許文献３）。
特開２００５－７２０６７ 特開２００７－２０４３２４ 国際公開第２００７／１００１４６号パンフレット 特開２００３－０４６０８１ A.Ohtomo et.al , Applied Physics Letters , Vol.72 , No.19 , 11 May 1998 , 2466-2468 Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77 H.Ryoken et.al., Journal of Crystal Growth 287(2006)134-138 In addition, transparent electronic devices have been studied focusing on oxide semiconductors. Since p-Si has a narrow band gap and generation of photocarriers due to light irradiation causes malfunction, a TFT made of p-Si requires a metal mask for blocking light. Therefore, light transmittance cannot be obtained with a TFT using p-Si. In contrast, a TFT using a semiconductor that does not absorb visible light is expected to operate normally without being affected by light. Currently, TFTs for liquid crystal panels are made of p-Si, and due to the presence of the metal mask, the proportion of the portion through which light can be transmitted is about 50%. Therefore, it is considered that this energy efficiency can be improved by obtaining a transparent TFT that does not require a metal mask.

On the other hand, there are reports that TFTs using zinc oxide are inferior in white reproducibility because the wavelength at the absorption edge is slightly visible, and there are opinions that polycrystalline zinc oxide is inferior in mobility.
In the Mg-containing ZnO mixed single crystal, when crystal growth is performed at a high temperature up to about 1000 ° C., the stable Mg / (Zn + Mg) ratio x that can be obtained thermodynamically is 0 <x <0.15 is known (H. Ryoken et.al., Journal of Crystal Growth 287 (2006) 134-138) (Non-Patent Document 3).
JP-A-2005-72067 JP2007-204324 International Publication No. 2007/100146 Pamphlet JP 2003-046081 A A.Ohtomo et.al, Applied Physics Letters, Vol.72, No.19, 11 May 1998, 2466-2468 Maki et al. Jpn. J. Appl. Phys. 42 (2003) 75-77 H. Ryoken et.al., Journal of Crystal Growth 287 (2006) 134-138

　ＺｎＯ水熱合成基板は鉱化剤に基づくＬｉが混入しており、これを基板としてＺｎＯ単結晶のＬＰＥ成長を行うとＬＰＥ成長膜側へＬｉが拡散する問題点があった。更には、ＬＰＥ成長法を用いて膜厚が厚いＺｎＯ単結晶を成長させた後、基板部分を研磨またはエッチングで除去しても成長膜側へＬｉが拡散するため、ＬＰＥ成長膜を自立化させてもＬｉに基づくデバイス特性の不安定化の問題点があった。更には、自立ＺｎＯ単結晶を作製するため、膜厚が厚いＺｎＯ単結晶のＬＰＥ成長を行うと、Ｐｔ冶工具を基点としたフラックス析出が起こり、フラックス析出部を基点とした成長中、冷却中および研削／研磨中のクラックが発生しやすいという問題点があった。
　このような背景の下、Ｌｉ濃度が低い自立ＺｎＯ単結晶を提供することが望まれている。
The ZnO hydrothermal synthesis substrate is mixed with Li based on the mineralizer, and when this is used as a substrate for the LPE growth of ZnO single crystal, there is a problem that Li diffuses to the LPE growth film side. Furthermore, after growing a thick ZnO single crystal using the LPE growth method, Li diffuses to the growth film side even if the substrate portion is removed by polishing or etching, so that the LPE growth film becomes self-supporting. However, there was a problem of destabilization of device characteristics based on Li. Furthermore, in order to produce a free-standing ZnO single crystal, when LPE growth of a thick ZnO single crystal is performed, flux precipitation occurs based on the Pt jig tool, and during growth and cooling based on the flux precipitation portion In addition, there is a problem that cracks are easily generated during grinding / polishing.
Under such circumstances, it is desired to provide a self-supporting ZnO single crystal having a low Li concentration.
　本発明者らは、自立化が可能なＺｎＯ系混晶単結晶およびその積層体を得るべく鋭意検討した。その結果、単に混晶層を成長させた後に基板を取り除くのみでは、得られた自立Ｍｇ含有ＺｎＯ混晶単結晶の表面と裏面とに僅かなバンドギャップ差がみとめられ、想定した光透過率を得ることができず、かつ、自立Ｍｇ含有ＺｎＯ混晶単結晶の表面と裏面とに不純物濃度の違いが認められ、これが、光物性や電気物性の変質をもたらす原因となるおそれがあることを見出した。この方法では、以下の問題点がある。図３を用いて説明する。高品質な結晶質Ａ－２の表面に、研磨、ないし、表面処理を施すことで生じた汚染層、ないし、結晶性劣化層であるＡ－３が存在する構成となった酸化亜鉛を基板として混晶結晶をＬＰＥ成長するため、成長後は、基板側の界面部であるＤ－３部は、成長層から拡散してきたＭｇや汚染層から拡散してきた不純物が存在する層となる。また、ＬＰＥ成長後の水熱合成基板は、高品質酸化亜鉛層Ｄ－１と拡散・汚染層Ｄ－３とで構成されるようになる。一方、混晶層を成長させる際、初期に成長した部分からは、水熱合成基板に対してＭｇが拡散し、かつ、基板の汚染層Ａ－３から不純物が拡散するために、基板側に拡散層Ｄ－３ができるのと同様に、混晶成長層側にもＭｇ濃度が低下し、不純物が混入した拡散層Ｄ－４が形成される。Ｄ－１および、Ｄ－３を取り除くのみでは、自立Ｍｇ含有ＺｎＯ混晶単結晶は、本来得るべきＬｉ汚染レベルが、１×１０１５個／ｃｍ３以下に保たれている混晶層Ｅ－２と、それを超えるＬｉ濃度を有し、かつ、Ｅ－２層よりも低いＭｇ濃度を持った拡散層Ｅ－４から構成されるものであった。これを近紫外線透明な基板として素子を形成すると、Ｅ－２に比べて、僅かにバンドギャップが狭められ、かつ、Ｌｉが多いＥ－４が原因となり、十分な光透過率が得られなかった。　このような背景の下、不純物として混入するＬｉも含め、均一な組成を有する自立Ｍｇ含有ＺｎＯ系混晶単結晶およびその積層体を提供することが望まれている。 The present inventors diligently studied to obtain a ZnO-based mixed crystal single crystal that can be self-supported and a laminate thereof. As a result, only by removing the substrate after growing the mixed crystal layer, a slight band gap difference is found between the front and back surfaces of the obtained self-standing Mg-containing ZnO mixed single crystal, and the assumed light transmittance is reduced. It has been found that there is a difference in impurity concentration between the front surface and the back surface of the free-standing Mg-containing ZnO mixed single crystal, and this may cause alteration of optical properties and electrical properties. It was. This method has the following problems. This will be described with reference to FIG. As a substrate, zinc oxide having a structure in which a contamination layer produced by polishing or surface treatment on the surface of high-quality crystalline A-2, or A-3 which is a crystalline deterioration layer is present is present. Since the mixed crystal is grown by LPE, after the growth, the D-3 portion which is the interface portion on the substrate side becomes a layer in which Mg diffused from the growth layer and impurities diffused from the contamination layer exist. Further, the hydrothermal synthesis substrate after the LPE growth is composed of a high quality zinc oxide layer D-1 and a diffusion / contamination layer D-3. On the other hand, when the mixed crystal layer is grown, Mg diffuses from the initially grown portion to the hydrothermal synthesis substrate, and impurities diffuse from the contaminated layer A-3 of the substrate. Similarly to the formation of the diffusion layer D-3, the Mg concentration is lowered on the mixed crystal growth layer side, and the diffusion layer D-4 mixed with impurities is formed. By simply removing D-1 and D-3, the self-standing Mg-containing ZnO mixed crystal single crystal has a mixed crystal layer E− in which the Li contamination level to be originally obtained is maintained at 1 × 10 15 pieces / cm 3 or less. 2 and a diffusion layer E-4 having a Li concentration exceeding that and a Mg concentration lower than that of the E-2 layer. When an element was formed using this as a near-ultraviolet transparent substrate, the band gap was slightly narrowed compared to E-2, and due to E-4 having a large amount of Li, sufficient light transmittance could not be obtained. . Under such a background, it is desired to provide a self-supporting Mg-containing ZnO mixed single crystal having a uniform composition including Li mixed as an impurity and a laminate thereof.
　上記課題は、以下の本発明によって解決することができる。
　本発明の第１の実施形態は、溶質であるＺｎＯと、溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＺｎＯ単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法である。前記溶媒は、ＰｂＯおよびＢｉ２Ｏ３の組み合わせであるか、ＰｂＦ２およびＰｂＯの組み合わせであることが好ましい。
　本発明の第２の実施形態は、上記本発明の第１の実施形態に記載のＺｎＯ単結晶の製造方法によって得られた自立ＺｎＯ単結晶ウエファーであって、膜厚が１００μｍ以上であることを特徴とする自立ＺｎＯ単結晶ウエファーである。　
　尚、本願明細書において、「自立」なる用語は、成長に用いた種結晶基板を研磨、および/または、エッチングで除去し、成長層のみからなることをいう。また、「連続的」なる用語は、種結晶基板を引上げる工程においてその引上げ速度が一定であることを意味し、「間欠的」なる用語は、種結晶基板を引上げる工程において引上げ速度が変化することを意味する。また、「溶質」なる用語は、溶液を作る際に溶媒に溶かす物質をいい、この「溶媒」なる用語は、溶液を作る際に溶かす物質の媒体となる物質をいう。 The above problems can be solved by the following present invention.
In the first embodiment of the present invention, ZnO as a solute and a solvent are mixed and melted, and then the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is continuously formed. And a step of growing the ZnO single crystal on the seed crystal substrate by pulling up periodically or intermittently. A method for producing a ZnO single crystal by a liquid phase epitaxial growth method. The solvent is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO.
The second embodiment of the present invention is a self-supporting ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment of the present invention, and has a film thickness of 100 μm or more. It is a free-standing ZnO single crystal wafer characterized.
In the present specification, the term “self-supporting” means that the seed crystal substrate used for growth is removed by polishing and / or etching and consists of only a growth layer. The term “continuous” means that the pulling rate is constant in the step of pulling up the seed crystal substrate, and the term “intermittent” means that the pulling rate changes in the step of pulling up the seed crystal substrate. It means to do. The term “solute” refers to a substance that dissolves in a solvent when a solution is made, and the term “solvent” refers to a substance that becomes a medium of a substance that is dissolved when a solution is made.

　本発明の第３の実施形態は、厚み５０μｍ以上の板状形状を有し、板の厚み方向、および、面内方向の何れに対しても均一なＺｎとＭｇの化学組成を有し、かつ、表裏面のうち少なくとも１面がエピタキシャル成長可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。
　本発明の第４の実施形態は、溶質であるＺｎＯおよびＭｇＯと、溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＭｇ含有ＺｎＯ系混晶単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＭｇ含有ＺｎＯ系混晶単結晶の製造方法である。前記溶媒は、ＰｂＯおよびＢｉ２Ｏ３の組み合わせであるか、ＰｂＦ２およびＰｂＯの組み合わせであることが好ましい。　本発明の第５の実施形態は、上記第４の実施形態に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーであって、厚み５０μｍ以上の板状形状を有し、板の厚み方向、および、面内方向の何れに対しても均一なＺｎとＭｇの化学組成を有し、かつ、表裏面のうち少なくとも１面がエピタキシャル成長可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。
　尚、本明細書において、「Ｍｇ含有ＺｎＯ系混晶単結晶」なる用語は、Ｚｎ１－ｘＭｇｘＯ（０＜ｘ＜０．１５）の組成を有する単結晶をいう。
The third embodiment of the present invention has a plate-like shape with a thickness of 50 μm or more, has a uniform chemical composition of Zn and Mg in both the thickness direction of the plate and the in-plane direction, and The self-standing Mg-containing ZnO mixed single crystal wafer is characterized in that at least one of the front and back surfaces has flatness capable of epitaxial growth.
The fourth embodiment of the present invention includes a step of directly contacting a seed crystal substrate with the obtained melt after mixing and melting ZnO and MgO, which are solutes, and a solvent, and the seed crystal substrate. And continuously growing the Mg-containing ZnO mixed crystal single crystal on the seed crystal substrate by continuously or intermittently pulling the Mg-containing ZnO mixed crystal single crystal by the liquid phase epitaxial growth method. It is a manufacturing method of a crystal. The solvent is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO. The fifth embodiment of the present invention is a self-supporting Mg-containing ZnO mixed single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment, and has a thickness of 50 μm. It has the above plate shape, has a uniform chemical composition of Zn and Mg in both the thickness direction and in-plane direction of the plate, and at least one of the front and back surfaces can be epitaxially grown It is a self-standing Mg-containing ZnO mixed single crystal wafer characterized by having flatness.
In this specification, the term “Mg-containing ZnO mixed crystal single crystal” refers to a single crystal having a composition of Zn 1-x Mg x O (0 <x <0.15).

　本発明の好ましい態様によれば、膜厚の厚いＺｎＯ単結晶を得ることができる。ＺｎＯ単結晶を成長させた後、種結晶基板を研磨またはエッチングで除去し、前記単結晶の液相エピタキシャル成長した－ｃ面側を研磨またはエッチングすることによりＬｉ濃度が低い自立ＺｎＯ単結晶が得られる。得られた自立ＺｎＯ単結晶は、そのままウエファーとして、あるいはＺｎＯ系混晶単結晶の種結晶基板などとして好適に用いられる。
　本発明の好ましい態様である自立ＺｎＯ単結晶ウエファーは、結晶性が高く、キャリヤ移動度を高く保持したままキャリヤ濃度を制御することができる。また、基板からのＬｉ拡散を低減でき、デバイス作動時の不安定稼動を抑制することが可能となる。更には、自立化しているため、＋ｃ面および－ｃ面の何れもデバイス作製基板表面に使用でき、目的とするデバイスに好適な成長面を選択できる。
According to a preferred aspect of the present invention, a thick ZnO single crystal can be obtained. After growing the ZnO single crystal, the seed crystal substrate is removed by polishing or etching, and the -c plane side of the single crystal subjected to liquid phase epitaxial growth is polished or etched to obtain a freestanding ZnO single crystal having a low Li concentration. . The obtained free-standing ZnO single crystal is suitably used as a wafer as it is or as a seed crystal substrate of a ZnO-based mixed crystal single crystal.
The free-standing ZnO single crystal wafer which is a preferred embodiment of the present invention has high crystallinity and can control the carrier concentration while maintaining high carrier mobility. In addition, Li diffusion from the substrate can be reduced, and unstable operation during device operation can be suppressed. Furthermore, since it is self-supporting, both the + c plane and the −c plane can be used as the surface of the device fabrication substrate, and a growth plane suitable for the target device can be selected.
また、本発明の好ましい態様によれば、ＺｎＯに比べてバンドギャップが広く、可視光から近紫外に対する透明性を担保した自立Ｍｇ含有ＺｎＯ系混晶単結晶が得られる。得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶は、単結晶であることから多結晶では得られない高い移動度の実現が可能であり、ウエファーなどとして好適に用いられる。

　本発明の好ましい態様の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーは、結晶性が高く、キャリヤ移動度を高く保持したままキャリヤを制御することができる。また、組成不均一層を除去しているため、ＺｎとＭｇの組成が均一となり、近紫外域での透過率を高くすることができるため、ＺｎＯを用いたＬＥＤ等の発光素子の光取出し効率を高くすることができる。また、基板からのＬｉ拡散を低減でき、デバイス作動時の不安定稼動を抑制することが可能となる上、Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有させることで電気伝導性を付与できる。更には、自立化しているため、+ｃ面および-ｃ面の何れもデバイス作製基板表面に利用でき、目的とするデバイスに好適な成長面を選択できる。以上の特性から、可視光に透明な透明ＴＦＴとして使用することも可能となる。本発明の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーは、今後、発展が見込まれる電子素子や光学素子に利用することができる。 Moreover, according to the preferable aspect of this invention, the band gap is wide compared with ZnO, and the self-supporting Mg containing ZnO type mixed crystal single crystal which ensured the transparency with respect to near ultraviolet from visible light is obtained. Since the obtained self-supporting Mg-containing ZnO-based mixed crystal single crystal is a single crystal, it can realize high mobility that cannot be obtained by polycrystal, and is preferably used as a wafer.

The self-supporting Mg-containing ZnO mixed single crystal wafer of a preferred embodiment of the present invention has high crystallinity and can control carriers while maintaining high carrier mobility. In addition, since the non-uniform composition layer is removed, the composition of Zn and Mg becomes uniform, and the transmittance in the near ultraviolet region can be increased. Therefore, the light extraction efficiency of light emitting elements such as LEDs using ZnO Can be high. In addition, Li diffusion from the substrate can be reduced, and unstable operation during device operation can be suppressed, and at least one selected from the group consisting of Al, Ga, In, H, and F is included. Can provide electrical conductivity. Furthermore, since it is self-supporting, both the + c plane and the −c plane can be used for the device fabrication substrate surface, and a growth plane suitable for the target device can be selected. From the above characteristics, it can be used as a transparent TFT transparent to visible light. The self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer of the present invention can be used for electronic elements and optical elements that are expected to develop in the future.
図１は、自立Ｍｇ含有ＺｎＯ系混晶単結晶製造時の問題点を説明するための模式的断面図である。FIG. 1 is a schematic cross-sectional view for explaining problems in producing a self-supporting Mg-containing ZnO mixed single crystal. 図２は、従来の素子構造および本発明で得られるＭｇ含有ＺｎＯ系混晶単結晶を用いた素子構造を表す構成図である。FIG. 2 is a configuration diagram showing a conventional element structure and an element structure using an Mg-containing ZnO mixed single crystal obtained by the present invention. 図３は、自立Ｍｇ含有ＺｎＯ系混晶単結晶製造時の問題点を説明するための模式的断面図である。FIG. 3 is a schematic cross-sectional view for explaining problems in the production of a self-supporting Mg-containing ZnO mixed single crystal. 図４は、本発明の実施例および比較例で使用した炉の構成図である。FIG. 4 is a block diagram of the furnace used in the examples and comparative examples of the present invention.
符号の説明Explanation of symbols
　１：上段ヒーター
　２：中断ヒーター
　３：下段ヒーター
　４：Ｐｔるつぼ
　５：引上軸
　６：基板ホルダー
　７：基板
　８：融液
　９：るつぼ台
　１０：熱電対
　１１：炉心管
　１２：炉蓋 1: Upper heater 2: Interruption heater 3: Lower heater 4: Pt crucible 5: Pulling shaft 6: Substrate holder 7: Substrate 8: Melt 9: Crucible stand 10: Thermocouple 11: Core tube 12: Furnace lid
　以下、本発明について詳細に説明する。
　本発明の第１の実施形態は、溶質であるＺｎＯと、溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＺｎＯ単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法である。 Hereinafter, the present invention will be described in detail.
In the first embodiment of the present invention, ZnO as a solute and a solvent are mixed and melted, and then the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is continuously formed. And a step of growing the ZnO single crystal on the seed crystal substrate by pulling up periodically or intermittently. A method for producing a ZnO single crystal by a liquid phase epitaxial growth method.

　自立ＺｎＯ単結晶を製造するためには、ＺｎＯ単結晶の厚膜成長が必要となる。製造した自立ＺｎＯ単結晶をその後のデバイス製造に供するためには、取扱い時クラック等が発生しない厚みを有する必要があり、その厚みは最低５０μｍ程度となる。種結晶基板の研磨後に得られた自立ＺｎＯ単結晶が５０μｍの厚みを有するためには、表裏面の研磨しろを考慮して１００μｍ程度以上の成長膜厚が必要となる。本発明者らが先に出願した「液相成長法によるＺｎＯ単結晶の製造方法」（国際公開第２００７／１００１４６号パンフレット）の方法を用いれば、１００μｍ以上の膜厚を有するＺｎＯ単結晶を成長させることができる。この方法では、Ｐｔ治工具を用いて水熱合成基板を保持し、基板表面を融液表面に接液することでエピタキシャル成長させる。しかし、Ｐｔ治工具は熱伝導性が高いため、Ｐｔ冶工具周辺の温度が低下し、その結果、Ｐｔ冶工具近傍でフラックス析出がしやすいことが判明した。フラックスが析出するとフラックス成分が成長膜中に取り込まれ、これを基点としたクラックが成長、冷却および研磨／エッチング中に発生し歩留が低下することが分かった。
In order to manufacture a free-standing ZnO single crystal, a thick film growth of the ZnO single crystal is required. In order to use the produced free-standing ZnO single crystal for subsequent device production, it is necessary to have a thickness that does not cause cracks or the like during handling, and the thickness is at least about 50 μm. In order for the free-standing ZnO single crystal obtained after polishing the seed crystal substrate to have a thickness of 50 μm, a growth film thickness of about 100 μm or more is required in consideration of the polishing margin on the front and back surfaces. By using the method of “Preparation of ZnO single crystal by liquid phase growth method” (International Publication No. 2007/100146 pamphlet) filed by the present inventors, a ZnO single crystal having a thickness of 100 μm or more is grown. Can be made. In this method, the hydrothermal synthesis substrate is held using a Pt jig and the substrate surface is brought into contact with the melt surface for epitaxial growth. However, since the Pt jig / tool has high thermal conductivity, it has been found that the temperature around the Pt jig / tool decreases, and as a result, flux precipitation tends to occur near the Pt / tool. It was found that when the flux is deposited, the flux component is taken into the growth film, and cracks based on this are generated during growth, cooling and polishing / etching, and the yield is lowered.

　この問題点を解決するため、本発明者らが鋭意研究したところ、成長中に種結晶基板を保持したＰｔ冶工具を連続的あるいは間欠的に引上げることで融液にＰｔ治工具が接触する時間を減らしたところ、膜中へのフラックス混入を低減でき、その結果、成長中および研磨／エッチング中のクラック発生を抑制できることがわかった。軸の引上げ手法としては、連続的あるいは間欠的何れも採用可能であるが、連続的軸引上げの方が安定成長の面で優れている。
In order to solve this problem, the present inventors have conducted intensive research. As a result, the Pt jig is brought into contact with the melt by continuously or intermittently pulling up the Pt jig holding the seed crystal substrate during growth. When the time was reduced, it was found that flux mixing into the film could be reduced, and as a result, generation of cracks during growth and polishing / etching could be suppressed. As the shaft pulling method, either continuous or intermittent can be adopted, but continuous shaft pulling is superior in terms of stable growth.

　連続的に種結晶基板を引上げる速度Ｖは、２μｍ／ｈｒ以上５０μｍ／ｈｒ以下が好適である。より好ましくは、４μｍ／ｈｒ以上２０μｍ／ｈｒ以下、更に好ましくは、６μｍ／ｈｒ以上１０μｍ／ｈｒ以下である。２μｍ／ｈｒ未満では、軸引上げによるフラックス巻き込み低減効果が少なく、５０μｍ／ｈｒを超えると基板が融液表面より離れる可能性がある。間欠的に種結晶基板を引上げる際は、その平均速度が上記の範囲となることが好ましい。すなわち、間欠的に種結晶基板を引上げる平均速度ｖは、２μｍ／ｈｒ以上５０μｍ／ｈｒ以下が好適であり、より好ましくは、４μｍ／ｈｒ以上２０μｍ／ｈｒ以下、更に好ましくは、６μｍ／ｈｒ以上１０μｍ／ｈｒ以下である。
The speed V for continuously pulling up the seed crystal substrate is preferably 2 μm / hr or more and 50 μm / hr or less. More preferably, it is 4 μm / hr or more and 20 μm / hr or less, and further preferably 6 μm / hr or more and 10 μm / hr or less. If it is less than 2 μm / hr, the effect of reducing the entrainment of flux by pulling up the shaft is small, and if it exceeds 50 μm / hr, the substrate may be separated from the melt surface. When the seed crystal substrate is pulled up intermittently, the average speed is preferably within the above range. That is, the average speed v for intermittently pulling up the seed crystal substrate is preferably 2 μm / hr or more and 50 μm / hr or less, more preferably 4 μm / hr or more and 20 μm / hr or less, and further preferably 6 μm / hr or more. 10 μm / hr or less.
　使用できる溶媒は、溶質であるＺｎＯを融解させることができるものであれば特に制限されないが、ＰｂＯおよびＢｉ２Ｏ３の組み合わせであるか、ＰｂＦ２およびＰｂＯの組み合わせであることが好ましい。上記溶質と、溶媒との混合比は、ＺｎＯのみに換算した溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％が好ましく、より好ましくは、溶質濃度が、５ｍｏｌ％以上１０ｍｏｌ％以下である。溶質濃度が、５ｍｏｌ％未満では成長速度が遅く、１０ｍｏｌ％を超えると成長温度が高くなり、溶媒蒸発量が多くなることがある。 The solvent that can be used is not particularly limited as long as it can melt the solute ZnO, but is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO. The mixing ratio of the solute and the solvent is preferably solute: solvent = 5-30 mol%: 95-70 mol% converted to ZnO alone, and more preferably the solute concentration is 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature increases and the amount of solvent evaporation may increase.

　本発明の好ましい態様では、溶質であるＺｎＯと、溶媒であるＰｂＯおよびＢｉ２Ｏ３とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＺｎＯ単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法である。本発明の好ましい態様では、上記溶質と、溶媒であるＰｂＯおよびＢｉ２Ｏ３との混合比が、溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％であり、溶媒であるＰｂＯとＢｉ２Ｏ３との混合比がＰｂＯ：Ｂｉ２Ｏ３＝０．１～９５ｍｏｌ％：９９．９～５ｍｏｌ％である。溶媒組成としては、より好ましくは、ＰｂＯ：Ｂｉ２Ｏ３＝３０～９０ｍｏｌ％：７０～１０ｍｏｌ％であり、特に好ましくは、ＰｂＯ：Ｂｉ２Ｏ３＝６０～８０ｍｏｌ％：４０～２０ｍｏｌ％である。ＰｂＯもしくはＢｉ２Ｏ３単独の溶媒では、液相成長温度が高くなるので、上記のような混合比を有するＰｂＯおよびＢｉ２Ｏ３混合溶媒が好適である。溶質であるＺｎＯと、溶媒であるＰｂＯおよびＢｉ２Ｏ３の混合比は、より好ましくは、溶質濃度が、５ｍｏｌ％以上１０ｍｏｌ％以下である。溶質濃度が、５ｍｏｌ％未満では成長速度が遅く、１０ｍｏｌ％を超えると成長温度が高くなることがある。
In a preferred embodiment of the present invention, after mixing and melting ZnO as a solute and PbO and Bi 2 O 3 as solvents, a step of bringing a seed crystal substrate into direct contact with the obtained melt, And a step of growing the ZnO single crystal on the seed crystal substrate by pulling the seed crystal substrate continuously or intermittently, and a method for producing a ZnO single crystal by a liquid phase epitaxial growth method. In a preferred embodiment of the present invention, the mixing ratio of the solute and the solvents PbO and Bi 2 O 3 is solute: solvent = 5 to 30 mol%: 95 to 70 mol%, and the solvent PbO and Bi 2 O. 3 is PbO: Bi 2 O 3 = 0.1 to 95 mol%: 99.9 to 5 mol%. The solvent composition is more preferably PbO: Bi 2 O 3 = 30 to 90 mol%: 70 to 10 mol%, and particularly preferably PbO: Bi 2 O 3 = 60 to 80 mol%: 40 to 20 mol%. . Since the liquid phase growth temperature becomes high in the solvent of PbO or Bi 2 O 3 alone, the PbO and Bi 2 O 3 mixed solvent having the above mixing ratio is preferable. The mixing ratio of ZnO as a solute and PbO and Bi 2 O 3 as solvents is more preferably a solute concentration of 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature may increase.

本発明の好ましい態様では、溶質であるＺｎＯと、溶媒であるＰｂＦ２およびＰｂＯとを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＺｎＯ単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法である。本発明の好ましい態様では、溶質であるＺｎＯと溶媒であるＰｂＦ２およびＰｂＯとの混合比が、溶質：溶媒＝２～２０ｍｏｌ％：９８～８０ｍｏｌ％であり、溶媒であるＰｂＦ２とＰｂＯとの混合比がＰｂＦ２：ＰｂＯ＝８０～２０ｍｏｌ％：２０～８０ｍｏｌ％である。溶媒の混合比が、ＰｂＦ２：ＰｂＯ＝８０～２０ｍｏｌ％：２０～８０ｍｏｌ％であると、溶媒であるＰｂＦ２およびＰｂＯの蒸発量を抑制でき、その結果、溶質濃度の変動が少なくなるので、安定的にＺｎＯ単結晶を成長させることができる。溶媒であるＰｂＦ２とＰｂＯとの混合比は、より好ましくはＰｂＦ２：ＰｂＯ＝６０～４０ｍｏｌ％：４０～６０ｍｏｌ％である。溶質であるＺｎＯと溶媒であるＰｂＦ２およびＰｂＯとの混合比は、溶質が５～１０ｍｏｌ％のときより好ましい。溶質濃度が５ｍｏｌ％未満では、成長速度が遅く、１０ｍｏｌ％を超えると、溶質成分を溶解させる温度が高くなり、溶媒蒸発量が多くなることがある。本発明では、液相成長法を用いる。同法は、気相成長法と異なり、真空系を必要とせず、そのため、低コストでＺｎＯ単結晶を製造することができる上、熱平衡成長であるため、高い結晶性を有するＺｎＯ単結晶を成長させることができる。また、過飽和度を制御することにより、成長速度を制御でき、比較的高い成長速度を実現できる。
In a preferred embodiment of the present invention, after mixing and melting ZnO as a solute and PbF 2 and PbO as a solvent, a seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal And a step of growing the ZnO single crystal on the seed crystal substrate by pulling the substrate continuously or intermittently. A method for producing a ZnO single crystal by a liquid phase epitaxial growth method. In a preferred embodiment of the present invention, the mixing ratio of the solute ZnO and the solvents PbF 2 and PbO is solute: solvent = 2 to 20 mol%: 98 to 80 mol%, and the solvent PbF 2 and PbO The mixing ratio is PbF 2 : PbO = 80 to 20 mol%: 20 to 80 mol%. When the solvent mixing ratio is PbF 2 : PbO = 80 to 20 mol%: 20 to 80 mol%, the amount of evaporation of the solvents PbF 2 and PbO can be suppressed, and as a result, fluctuations in the solute concentration are reduced. A ZnO single crystal can be stably grown. The mixing ratio of the solvent PbF 2 and PbO is more preferably PbF 2 : PbO = 60 to 40 mol%: 40 to 60 mol%. The mixing ratio of ZnO as the solute and PbF 2 and PbO as the solvent is more preferable when the solute is 5 to 10 mol%. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the temperature at which the solute component is dissolved increases and the amount of solvent evaporation may increase. In the present invention, a liquid phase growth method is used. Unlike the vapor phase growth method, this method does not require a vacuum system, so that it is possible to produce a ZnO single crystal at low cost and to grow a ZnO single crystal having high crystallinity because of thermal equilibrium growth. Can be made. Further, by controlling the degree of supersaturation, the growth rate can be controlled, and a relatively high growth rate can be realized.

　本発明の好ましい態様では、上記ＺｎＯ単結晶が、少量の異種元素を含む。ＺｎＯは、異種元素をドーピングすることでその特性を発現・変化させることができる。本発明の好ましい態様では、Ｌｉ、Ｎａ、Ｋ、Ｃｓ、Ｒｂ、Ｂｅ、Ｃａ、Ｓｒ、Ｂａ、Ｃｕ、Ａｇ、Ｎ、Ｐ、Ａｓ、Ｓｂ、Ｂｉ、Ｂ、Ｔｌ、Ｃｌ、Ｂｒ、Ｉ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｄ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗおよびランタノイド元素等からなる群より選択される１以上を添加する。添加量は、溶質として使用されるＺｎＯに対して２０ｍｏｌ％以下、好ましくは１０ｍｏｌ％以下、より好ましくは１ｍｏｌ％以下である。異種元素を添加することにより、ｐ型半導体、ｎ型半導体、磁性半導体、導電率の制御、バリスタ応用、圧電体応用、電界発光素子および透明ＴＦＴへの応用等がある。
In a preferred embodiment of the present invention, the ZnO single crystal contains a small amount of a different element. ZnO can exhibit and change its characteristics by doping with different elements. In a preferred embodiment of the present invention, Li, Na, K, Cs, Rb, Be, Ca, Sr, Ba, Cu, Ag, N, P, As, Sb, Bi, B, Tl, Cl, Br, I, Mn One or more selected from the group consisting of Fe, Co, Ni, Cd, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and a lanthanoid element are added. The addition amount is 20 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, with respect to ZnO used as a solute. By adding different kinds of elements, there are p-type semiconductors, n-type semiconductors, magnetic semiconductors, conductivity control, varistor applications, piezoelectric body applications, electroluminescent elements, and transparent TFTs.

　本発明の好ましい態様では、成長用基板である種結晶基板としてＺｎＯ単結晶を用いる。ＺｎＯ単結晶成長用基板としては、ＺｎＯと同類の結晶構造を持ち、成長薄膜と基板とが反応しないものであれば使用可能である。例えば、サファイヤ、ＬｉＧａＯ２、ＬｉＡｌＯ２、ＬｉＮｂＯ３、ＬｉＴａＯ３、ＳｃＡｌＭｇＯ４、ＧａＮ、ＺｎＯなどが挙げられる。しかしながら、本発明における目的単結晶がＺｎＯ単結晶であることを考慮すると、基板と成長結晶の格子整合度が高いＺｎＯ基板を用いたホモエピタキシャル成長が結晶性、歪みの低減、成長膜の反りの低減および基板からの不純物拡散量低減の面で好ましい。
In a preferred embodiment of the present invention, a ZnO single crystal is used as a seed crystal substrate that is a growth substrate. As a substrate for ZnO single crystal growth, any substrate can be used as long as it has a crystal structure similar to ZnO and the grown thin film does not react with the substrate. Examples thereof include sapphire, LiGaO 2 , LiAlO 2 , LiNbO 3 , LiTaO 3 , ScAlMgO 4 , GaN, and ZnO. However, considering that the target single crystal in the present invention is a ZnO single crystal, homoepitaxial growth using a ZnO substrate having a high degree of lattice matching between the substrate and the grown crystal reduces crystallinity, distortion, and warpage of the grown film. And it is preferable in terms of reducing the amount of impurity diffusion from the substrate.

　本発明の好ましい態様では、ＺｎＯ単結晶の成長方位は＋ｃ面である。
　本発明の好ましい態様では、種結晶基板上にＺｎＯ単結晶を成長させた後、成長に用いた種結晶基板を研磨あるいはエッチングで除去することで自立化させることができる。その際、成長基板に近い－ｃ面側を少なくとも１０μｍ、好ましくは２０μｍ以上除去することで基板側からのＬｉ拡散層を除去することが可能となる。基板除去方法としては、研磨あるいはエッチング何れの方法も採用可能であるが、膜厚管理しやすい研削＋研磨が好適である。水熱合成基板上にＺｎＯ単結晶を成長させる。研磨またはエッチング後で５０μｍ程度の膜厚とするためには、成長段階で１００μｍ程度の膜厚が必要となる。成長後、基板側をセラミックスプレートにＷＡＸ固定を行い、研削器にて液相エピタキシャル成長面を平坦化することができる。ＬＰＥ面側（＋ｃ面）をセラミックスプレートに張替え、研削器にて基板厚相当を研削除去することで液相エピタキシャル成長膜だけとし、表裏面をラップおよびポリッシュすることで研磨してもよい。このとき、ＬＰＥ成長膜の水熱合成基板側は好ましくは１０μｍ、より好ましくは２０μｍ以上研磨することで水熱合成基板からのＬｉ拡散層を除去することが可能となる。
In a preferred embodiment of the present invention, the growth orientation of the ZnO single crystal is the + c plane.
In a preferred embodiment of the present invention, after growing a ZnO single crystal on a seed crystal substrate, the seed crystal substrate used for the growth can be made independent by polishing or etching. At that time, the Li diffusion layer from the substrate side can be removed by removing at least 10 μm, preferably 20 μm or more, on the −c plane side close to the growth substrate. As a substrate removing method, any method of polishing or etching can be adopted, but grinding + polishing which allows easy film thickness management is preferable. A ZnO single crystal is grown on a hydrothermal synthesis substrate. In order to obtain a film thickness of about 50 μm after polishing or etching, a film thickness of about 100 μm is required at the growth stage. After the growth, the substrate side is fixed to the ceramic plate by WAX, and the liquid phase epitaxial growth surface can be flattened by a grinder. The LPE surface side (+ c surface) may be replaced with a ceramic plate, and the substrate thickness may be ground and removed by a grinder to obtain only a liquid phase epitaxial growth film, and polishing may be performed by lapping and polishing the front and back surfaces. At this time, it is possible to remove the Li diffusion layer from the hydrothermal synthesis substrate by polishing the hydrothermal synthesis substrate side of the LPE growth film preferably at 10 μm, more preferably 20 μm or more.

　本発明の好ましい態様では、上記ＺｎＯ単結晶にＡｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有させる。Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有することにより、電気伝導性を発現することが可能となる。研磨やエッチング等により成長で用いた基板を除去すれば、自立導電性基板となり、電子素子や光学素子の表裏に電極を形成することができる。
In a preferred embodiment of the present invention, the ZnO single crystal contains one or more selected from the group consisting of Al, Ga, In, H and F. By containing one or more selected from the group consisting of Al, Ga, In, H, and F, it becomes possible to develop electrical conductivity. If the substrate used for growth is removed by polishing, etching, or the like, a self-supporting conductive substrate is formed, and electrodes can be formed on the front and back of the electronic element and the optical element.

　本発明の第２の実施形態は、上記本発明の第１の実施形態に記載のＺｎＯ単結晶の製造方法によって得られた自立ＺｎＯ単結晶ウエファーであって、膜厚が１００μｍ以上であることを特徴とする自立ＺｎＯ単結晶ウエファーである。厚みが１００μｍ未満では研磨後の厚みとして５０μｍを確保できず、その後のデバイス工程に供するのが困難となる。厚みの上限は規定されないが、５００μｍを超えると成長時間が長くなる。
The second embodiment of the present invention is a self-supporting ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment of the present invention, and has a film thickness of 100 μm or more. It is a free-standing ZnO single crystal wafer characterized. If the thickness is less than 100 μm, 50 μm cannot be ensured as the thickness after polishing, and it is difficult to use in subsequent device processes. The upper limit of the thickness is not specified, but if it exceeds 500 μm, the growth time becomes longer.

　本発明の好ましい態様では、第１の実施形態に記載のＺｎＯ単結晶の製造方法によって得られた自立ＺｎＯ単結晶ウエファーのＬｉ濃度は、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、好ましくは１×１０１５個／ｃｍ３以下、より好ましくは１×１０１４　個／ｃｍ３以下である。ここで、Ｌｉ濃度が１×１０１５個／ｃｍ３以下で均一であるとは、デバイス動作を不安定化するＬｉ濃度が自立化膜全体で１×１０１５個／ｃｍ３以下であることを意味する。Ｌｉ濃度の均一性は、次のようにして求めることができる。自立化処理後の表裏面数点のＬｉ濃度をダイナミックＳＩＭＳで測定することで表裏面内Ｌｉ濃度均一性を、更に、表裏面Ｌｉ濃度均一性測定済みサンプルをｃ面に垂直に切断した断面のＬｉ濃度をダイナミックスＳＩＭＳで測定することで膜厚方向のＬｉ濃度均一性を判断することができる。
In a preferred aspect of the present invention, the Li concentration of the free-standing ZnO single crystal wafer obtained by the method for producing a ZnO single crystal described in the first embodiment is uniform in the in-plane direction and the thickness direction of the wafer. And, Preferably it is 1 * 10 < 15 > piece / cm < 3 > or less, More preferably, it is 1 * 10 < 14 > piece / cm < 3 > or less. Here, when the Li concentration is uniform at 1 × 10 15 pieces / cm 3 or less, the Li concentration that destabilizes the device operation is 1 × 10 15 pieces / cm 3 or less in the entire self-supporting film. means. The uniformity of the Li concentration can be obtained as follows. By measuring the Li concentration at several points on the front and back surfaces after the self-supporting treatment by dynamic SIMS, the Li concentration uniformity in the front and back surfaces was further measured. The Li concentration uniformity in the film thickness direction can be determined by measuring the Li concentration by dynamics SIMS.

　本発明の好ましい態様では、上記自立ＺｎＯ単結晶ウエファーの表裏面少なくとも１面の平坦性は、エピタキシャル成長可能な程度であればよい。例えば、ＺｎＯ単結晶ウエファーの任意の位置において５０μｍ四方の表面粗さＲａが０．５ｎｍ以下であることが好ましく、更に好ましくは０．３ｎｍ以下である。０．５ｎｍを超えるとＬＥＤ成長膜が３次元成長したり、ピット不良が増える傾向があるので好ましくない。一方、表裏面の平坦性はできるだけ近い方が好ましい。表面と裏面とで平坦性が異なると、反りの発生要因となる。表面粗さＲａは、自立膜中央部５０μｍ四方について原子間力顕微鏡（Atomic Force Microscopy：ＡＦＭ）を用いることにより測定することができる。
In a preferred embodiment of the present invention, the flatness of at least one surface of the free-standing ZnO single crystal wafer may be such that it can be epitaxially grown. For example, the surface roughness Ra of 50 μm square at an arbitrary position of the ZnO single crystal wafer is preferably 0.5 nm or less, more preferably 0.3 nm or less. If it exceeds 0.5 nm, the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable. On the other hand, the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping. The surface roughness Ra can be measured by using an atomic force microscope (AFM) with respect to a 50 μm square of the free-standing film central part.
　本発明の好ましい態様では、上記自立ＺｎＯ単結晶ウエファーはＧａを含有することが好ましく、キャリヤ濃度が２．０×１０１７個／ｃｍ３～１．０×１０１９個／ｃｍ３であり、かつ、好ましくはＬｉ濃度が１×１０１５個／ｃｍ３以下、更に好ましくは１×１０１４個／ｃｍ３以下であることが好ましい。
　また、本発明の他の好ましい態様では、上記自立ＺｎＯ単結晶ウエファーはＡｌを含有し、キャリヤ濃度が２．０×１０１７個／ｃｍ３～１．０×１０１９個／ｃｍ３であり、かつ、好ましくはＬｉ濃度が１×１０１５個／ｃｍ３以下、更に好ましくは１×１０１４個／ｃｍ３以下であることが好ましい。

　更に、本発明の他の好ましい態様では、上記自立ＺｎＯ単結晶ウエファーはＩｎを含有し、キャリヤ濃度が２．０×１０１７個／ｃｍ３～３．５×１０１７個／ｃｍ３であり、かつ、好ましくはＬｉ濃度が１×１０１５個／ｃｍ３以下、更に好ましくは１×１０１４個／ｃｍ３以下であることが好ましい。
　本明細書において「キャリヤ濃度」および「キャリヤ移動度」は、東陽テクニカ製ホール効果・比抵抗測定装置を用い、Ｖａｎ　Ｄｅｒ　Ｐａｕｗ法により室温で測定することができる。 In a preferred embodiment of the present invention, the free-standing ZnO single crystal wafer preferably contains Ga, has a carrier concentration of 2.0 × 10 17 pieces / cm 3 to 1.0 × 10 19 pieces / cm 3 , and The Li concentration is preferably 1 × 10 15 atoms / cm 3 or less, more preferably 1 × 10 14 atoms / cm 3 or less.
In another preferred embodiment of the present invention, the self-supporting ZnO single crystal wafer contains Al and has a carrier concentration of 2.0 × 10 17 pieces / cm 3 to 1.0 × 10 19 pieces / cm 3 , And it is preferable that Li concentration is 1 * 10 < 15 > piece / cm < 3 > or less, More preferably, it is 1 * 10 < 14 > piece / cm < 3 > or less.

Furthermore, in another preferred embodiment of the present invention, the self-supporting ZnO single crystal wafer contains In and has a carrier concentration of 2.0 × 10 17 pieces / cm 3 to 3.5 × 10 17 pieces / cm 3 , And it is preferable that Li concentration is 1 * 10 < 15 > piece / cm < 3 > or less, More preferably, it is 1 * 10 < 14 > piece / cm < 3 > or less.
In the present specification, “carrier concentration” and “carrier mobility” can be measured at room temperature by the Van Der Pauw method using a Hall effect / specific resistance measuring device manufactured by Toyo Technica.
　本発明の第３の実施形態は、厚み５０μｍ以上の板状形状を有し、板の厚み方向、および、面内方向の何れに対しても均一なＺｎとＭｇの化学組成を有し、表裏面のうち少なくとも1面がエピタキシャル成長用基板として利用可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。厚みが５０μｍ未満では取り扱うのが困難となるため好ましくない。厚みの上限は特にされないが、５００μｍを超えると成長時間が長くなる。自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの膜厚方向、および、面内方向の組成均一性は、好ましくは±１０％以内、更に好ましくは±５％以内である。組成均一性が±１０％を超えると近紫外域での透過率が減少するので好ましくない。
　本発明において、面内方向の組成均一性は、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの表裏面のＭｇ／（Ｚｎ＋Ｍｇ）組成の均一性で評価され、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの表裏面におけるＰＬ発光波長分布を測定することで求めることができる。
　また、膜厚方向の組成均一性は、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの膜厚方向のＭｇ／（Ｚｎ＋Ｍｇ）組成の均一性で評価され、上記表裏面ＰＬ発光波長分布測定済みサンプルをｃ面に垂直に切断した断面のＣＬ（Cathode Luminescence；電子線励起発光スペクトル測定）発光波長分布を測定することで求めることができる。
　自立Ｍｇ含有ＺｎＯ混晶単結晶ウエファーの表裏面うち少なくとも１面の平坦性は、エピタキシャル成長可能な程度であればよい。例えば、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの任意の位置において５０μｍ四方の表面粗さＲａが０．５ｎｍ以下であることが好ましく、更に好ましくは０．３ｎｍｍ以下である。０．５ｎｍを超えるとＬＥＤ成長膜が３次元成長したり、ピット不良が増える傾向があるので好ましくない。一方、表裏面の平坦性はできるだけ近い方が好ましい。表面と裏面とで平坦性が異なると、反りの発生要因となる。表面粗さＲａは、自立膜中央部５０μｍ四方について原子間力顕微鏡（Atomic Force Microscopy：ＡＦＭ）を用いることにより測定することができる。 The third embodiment of the present invention has a plate-like shape with a thickness of 50 μm or more, has a uniform chemical composition of Zn and Mg in both the thickness direction and the in-plane direction of the plate, A self-standing Mg-containing ZnO mixed single crystal wafer characterized in that at least one of the back surfaces has flatness that can be used as a substrate for epitaxial growth. A thickness of less than 50 μm is not preferable because it becomes difficult to handle. The upper limit of the thickness is not particularly limited, but if it exceeds 500 μm, the growth time becomes long. The composition uniformity in the film thickness direction and in-plane direction of the self-supporting Mg-containing ZnO mixed single crystal wafer is preferably within ± 10%, more preferably within ± 5%. If the composition uniformity exceeds ± 10%, the transmittance in the near ultraviolet region decreases, which is not preferable.
In the present invention, the composition uniformity in the in-plane direction is evaluated by the uniformity of the Mg / (Zn + Mg) composition on the front and back surfaces of the self-supporting Mg-containing ZnO mixed single crystal wafer. It can obtain | require by measuring PL light emission wavelength distribution in front and back.
Further, the composition uniformity in the film thickness direction is evaluated by the uniformity of the Mg / (Zn + Mg) composition in the film thickness direction of the self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer. It can be obtained by measuring CL (Cathode Luminescence; electron beam excitation emission spectrum measurement) emission wavelength distribution of a section cut perpendicular to the c-plane.
The flatness of at least one of the front and back surfaces of the self-supporting Mg-containing ZnO mixed crystal single crystal wafer may be such that epitaxial growth is possible. For example, the surface roughness Ra of 50 μm square is preferably 0.5 nm or less, more preferably 0.3 nm or less, at an arbitrary position of the self-supporting Mg-containing ZnO mixed single crystal wafer. If it exceeds 0.5 nm, the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable. On the other hand, the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping. The surface roughness Ra can be measured by using an atomic force microscope (AFM) with respect to a 50 μm square of the free-standing film central part.

　本発明の好ましい実施形態は、バンドギャップ（Ｅｇ）値がウエファーの面内方向、および、厚み方向に対して均一であり、かつ、３．３０ｅＶを超える自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。ここで、バンドギャップ（Ｅｇ）値の均一性は、ＰＬおよびＣＬ発光波長から求めることができ、バンドギャップ（Ｅｇ）値は、好ましくは±６％以内、更に好ましくは±３％以内である。
A preferred embodiment of the present invention is a self-standing Mg-containing ZnO mixed single crystal wafer having a band gap (Eg) value that is uniform in the in-plane direction and the thickness direction of the wafer and exceeds 3.30 eV. is there. Here, the uniformity of the band gap (Eg) value can be determined from the PL and CL emission wavelengths, and the band gap (Eg) value is preferably within ± 6%, more preferably within ± 3%.

　ＺｎＯ系混晶単結晶のバンドギャップを制御するためには、ＺｎＯとＭｇＯあるいはＢｅＯを混晶化することで実現できるが、毒性等を考慮するとＭｇＯを混晶化することが好適である。ＺｎＯ系混晶単結晶のバンドギャップが３．３０ｅＶを下回るようではＭｇＯの混晶化率が低くなるので好ましくない。
In order to control the band gap of a ZnO-based mixed crystal single crystal, it can be realized by mixing ZnO and MgO or BeO. However, considering toxicity and the like, it is preferable to mix MgO. If the band gap of the ZnO-based mixed crystal single crystal is less than 3.30 eV, the MgO mixed crystallization rate is low, which is not preferable.

　上記バンドギャップ（Ｅｇ）は、本発明によって得られたＭｇ含有ＺｎＯ系混晶単結晶のＰＬおよびＣＬ発光波長を測定し、以下の式を用いることにより求めることができる。　
　Ｅｇ［ｅＶ］＝１．２４／ＰＬ（ＣＬ）発光波長［ｎｍ］＊１０００
The band gap (Eg) can be determined by measuring the PL and CL emission wavelengths of the Mg-containing ZnO mixed crystal single crystal obtained by the present invention and using the following equation.
Eg [eV] = 1.24 / PL (CL) emission wavelength [nm] * 1000

　ＰＬ発光波長の測定方法は、特に限定されるものではないが、本発明においては、Ａｃｃｅｎｔ社製ｒｐｍ２０００を使用し、励起レーザーはＨｅ－Ｃｄレーザー（λ＝３２５ｎｍ）を用い、室温（３００Ｋ）にて測定した値に基づいている。
　ＣＬ発光波長の測定法は、特に限定されるものでないが、本発明においては、５ＫｅＶの電子線を励起源に用い、室温にて測定した値に基づいている。
The method for measuring the PL emission wavelength is not particularly limited. In the present invention, the rpm 2000 manufactured by Accent is used, the excitation laser is a He—Cd laser (λ = 325 nm), and the room temperature (300 K) is used. Based on measured values.
The method for measuring the CL emission wavelength is not particularly limited, but in the present invention, it is based on a value measured at room temperature using a 5 KeV electron beam as an excitation source.

　本発明の好ましい態様において、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーは、Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有する。Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有することにより、電気伝導性を発現することが可能となる。研磨やエッチング等により成長で用いた基板を除去すれば、電子素子や光学素子の表裏面に電極を形成することができる。従って、自立化した導電性があるＭｇ含有ＺｎＯ系混晶単結晶を提供できることになる。このように導電性を有する自立Ｍｇ含有ＺｎＯ系混晶単結晶は、ＺｎＯ－ＬＥＤデバイスにおいてＬＥＤ光に透明で、格子整合し、導電性を持つ基板とすることができる。
In a preferred embodiment of the present invention, the self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer contains one or more selected from the group consisting of Al, Ga, In, H and F. By containing one or more selected from the group consisting of Al, Ga, In, H, and F, it becomes possible to develop electrical conductivity. If the substrate used for growth is removed by polishing, etching, or the like, electrodes can be formed on the front and back surfaces of the electronic element or optical element. Accordingly, it is possible to provide a Mg-containing ZnO mixed single crystal having self-supporting conductivity. Thus, the self-supporting Mg-containing ZnO mixed single crystal having conductivity is transparent to LED light in a ZnO-LED device, and can be a lattice-matched substrate having conductivity.

　本発明の好ましい実施形態において、Ｌｉ濃度は、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、好ましくは１×１０１５個／ｃｍ３以下、更に好ましくは1×１０14個／ｃｍ３以下である自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。ここで、Ｌｉ濃度が１×１０１５個／ｃｍ３以下で均一であるとは、デバイス動作を不安定化するＬｉ濃度が自立化膜全体で１×１０１５個／ｃｍ３以下であることを意味する。
Ｌｉ濃度の均一性は、次のようにして求めることができる。自立化処理後の表裏面数点のＬｉ濃度をダイナミックＳＩＭＳで測定することで表裏面内Ｌｉ濃度均一性を、更に、表裏面Ｌｉ濃度均一性測定済みサンプルをｃ面に垂直に切断した断面のＬｉ濃度をダイナミックスＳＩＭＳで測定することで膜厚方向のＬｉ濃度均一性を判断することができる。尚、本明細書において、ダイナミックＳＩＭＳ分析は、Ｃａｍｅｃａ製装置を用いて、一次イオン種；Ｏ２＋、一次イオン加速電圧；８ＫｅＶ、測定温度；室温の条件下で行う。
In a preferred embodiment of the present invention, the Li concentration is uniform in the in-plane direction and the thickness direction of the wafer, and is preferably 1 × 10 15 pieces / cm 3 or less, more preferably 1 × 10 14 pieces. This is a self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer of / cm 3 or less. Here, when the Li concentration is uniform at 1 × 10 15 pieces / cm 3 or less, the Li concentration that destabilizes the device operation is 1 × 10 15 pieces / cm 3 or less in the entire self-supporting film. means.
The uniformity of the Li concentration can be obtained as follows. By measuring the Li concentration at several points on the front and back surfaces after the self-supporting treatment by dynamic SIMS, the Li concentration uniformity in the front and back surfaces was further measured. The Li concentration uniformity in the film thickness direction can be determined by measuring the Li concentration by dynamics SIMS. In this specification, the dynamic SIMS analysis is performed under the conditions of primary ion species; O 2+ , primary ion acceleration voltage; 8 KeV, measurement temperature;
　尚、液相エピタキシャル成長時に使用する水熱合成基板は、１×１０１５から１×１０１７個／ｃｍ３程度のＬｉが含まれている。本発明の出願時点においては、ＬＰＥ成長法で高結晶性の結晶成長を実現するには、水熱合成によって育成された単結晶を用いるしか、手段はない。他に、気相成長単結晶などがあるが、その結晶性については必ずしも高い品質のものが手に入るとは限らず、現状、水熱合成ＺｎＯ単結晶のみが機能する基板材料である。そのため、それに特徴的なＬｉ不純物への対策が必要となる。仮に、高品質、高純度の単結晶基板の入手が容易になった場合、ＬＰＥ成長膜の水熱合成基板側（－ｃ面側）を好ましくは１０μｍ、更に好ましくは２０μｍ以上研磨する工程を省略することは可能であるが、Ｍｇの基板への拡散によって、基板と膜との間の中間層に、Ｍｇ濃度が一定ではない領域が生じることがあるため、同様に、ＬＰＥ成長膜の水熱合成基板側（－ｃ面側）を好ましくは１０μｍ、更に好ましくは２０μｍ以上研磨することが好適である。上述したように、水熱合成基板を用いて液相エピタキシャル成長を行うと、水熱合成基板からのＬｉ拡散が起こり、デバイス動作を不安定にしていた。液相エピタキシャル成長では、原料中にＬｉをほとんど含まないため、成長膜中にＬｉが混入しにくいが、基板や基板表面のＬｉ濃縮層から熱拡散する懸念があった。本発明者らが鋭意研究した結果、ＬＰＥ成長膜の水熱合成基板側の成長裏面側（－ｃ面）を好ましくは１０μｍ以上、より好ましくは２０μｍ以上研磨すれば、液相エピタキシャル成長膜中のＬｉ濃度を１×１０１５個／ｃｍ３以下にすることを見出した。また、それによって得られるＭｇ含有ＺｎＯ混晶単結晶ウエファーに用いれば、Ｌｉに基づくデバイス特性の不安定化を抑制することが可能となる。 In addition, the hydrothermal synthetic substrate used at the time of liquid phase epitaxial growth contains about 1 × 10 15 to 1 × 10 17 pieces / cm 3 of Li. At the time of filing of the present invention, the only way to achieve high crystal growth by the LPE growth method is to use a single crystal grown by hydrothermal synthesis. In addition, there are vapor grown single crystals and the like, but the crystal quality is not necessarily high quality, and at present, only a hydrothermally synthesized ZnO single crystal is a functional substrate material. Therefore, it is necessary to take measures against the Li impurity that is characteristic of it. If it is easy to obtain a high-quality, high-purity single crystal substrate, the step of polishing the LPE growth film on the hydrothermal synthesis substrate side (-c surface side) is preferably 10 μm, more preferably 20 μm or more. However, the diffusion of Mg to the substrate may cause a region where the Mg concentration is not constant in the intermediate layer between the substrate and the film. The synthetic substrate side (−c surface side) is preferably polished at 10 μm, more preferably 20 μm or more. As described above, when liquid phase epitaxial growth is performed using a hydrothermal synthetic substrate, Li diffusion from the hydrothermal synthetic substrate occurs, resulting in unstable device operation. In the liquid phase epitaxial growth, since Li is hardly contained in the raw material, it is difficult for Li to be mixed into the growth film, but there is a concern that the substrate may be thermally diffused from the Li concentrated layer on the substrate surface. As a result of intensive studies by the present inventors, if the growth back surface side (-c surface) of the LPE growth film on the hydrothermal synthesis substrate side is polished preferably by 10 μm or more, more preferably by 20 μm or more, Li in the liquid phase epitaxial growth film can be obtained. It was found that the concentration was 1 × 10 15 pieces / cm 3 or less. Moreover, if it is used for the Mg-containing ZnO mixed crystal single crystal wafer obtained thereby, it becomes possible to suppress destabilization of device characteristics based on Li.

　本発明の第４の実施形態は、溶質であるＺｎＯおよびＭｇＯと、溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＭｇ含有ＺｎＯ系混晶単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＭｇ含有ＺｎＯ系混晶単結晶の製造方法である。
The fourth embodiment of the present invention includes a step of directly contacting a seed crystal substrate with the obtained melt after mixing and melting ZnO and MgO, which are solutes, and a solvent, and the seed crystal substrate. And continuously growing the Mg-containing ZnO mixed crystal single crystal on the seed crystal substrate by continuously or intermittently pulling the Mg-containing ZnO mixed crystal single crystal by the liquid phase epitaxial growth method. It is a manufacturing method of a crystal.

　自立Ｍｇ含有ＺｎＯ系混晶単結晶を製造するためには、Ｍｇ含有ＺｎＯ系混晶単結晶の厚膜成長が必要となる。研磨後で５０μｍ厚の自立Ｍｇ含有ＺｎＯ混晶単結晶とするためには、表裏面の研磨しろを考慮して１００μｍ程度以上の成長膜厚が必要となる。本発明者らは、これまでに溶質であるＺｎＯおよびＭｇＯと、溶媒であるＰｂＯおよびＢｉ２Ｏ３とを混合して融解させた後、得られた融液に、種結晶または基板を直接接触させ、成長時間や成長中の温度降下速度を適宜調整するにより、あるいは、溶質であるＺｎＯおよびＭｇＯと、溶媒であるＰｂＦ２およびＰｂＯとを混合して融解させた後、得られた融液に、種結晶または基板を直接接触させ、成長時間や成長中の温度降下速度を適宜調整するにより、液相エピタキシャル成長法により１００μｍ以上の膜厚を有するＭｇ含有ＺｎＯ系混晶単結晶を成長させることができることを見出した。この方法では、Ｐｔ治工具を用いて水熱合成基板を保持し、基板表面を融液表面に接液することでエピタキシャル成長させる。しかし、Ｐｔ治工具は熱伝導性が高いため、Ｐｔ冶工具近傍でフラックス析出がしやすいことが判明した。フラックスが析出するとフラックス成分が成長膜中に取り込まれ、これを基点としたクラックが成長し、冷却および研磨／エッチング中に発生し歩留が低下することが分かった。
In order to produce a self-supporting Mg-containing ZnO mixed crystal single crystal, a thick film growth of the Mg-containing ZnO mixed crystal single crystal is required. In order to obtain a self-supporting Mg-containing ZnO mixed single crystal having a thickness of 50 μm after polishing, a growth film thickness of about 100 μm or more is required in consideration of the polishing margin on the front and back surfaces. The present inventors mixed ZnO and MgO as solutes so far with PbO and Bi 2 O 3 as solvents and melted them, and then contacted the seed crystal or the substrate directly with the obtained melt. Then, by appropriately adjusting the growth time and the temperature drop rate during growth, or by mixing and melting the solute ZnO and MgO and the solvents PbF 2 and PbO, the obtained melt The Mg-containing ZnO mixed crystal single crystal having a film thickness of 100 μm or more can be grown by liquid phase epitaxy by directly contacting the seed crystal or the substrate and appropriately adjusting the growth time and the temperature drop rate during the growth. I found out that I can do it. In this method, the hydrothermal synthesis substrate is held using a Pt jig and the substrate surface is brought into contact with the melt surface for epitaxial growth. However, it has been found that since the Pt jig / tool has high thermal conductivity, flux precipitation is likely to occur near the Pt jig / tool. It has been found that when the flux is deposited, the flux component is taken into the growth film, cracks based on this grow, and are generated during cooling and polishing / etching, resulting in a decrease in yield.

　この問題点を解決するため、本発明者らが鋭意研究したところ、成長中に基板を保持したＰｔ冶工具を連続的あるいは間欠的に引上げることで融液にＰｔ治工具が接触する時間を減らしたところ膜中へのフラックス混入を低減でき、その結果、成長中および研磨／エッチング中のクラック発生を抑制することが可能となることを見出した。軸の引上げ手法としては、連続的あるいは間欠的何れも採用可能であるが、連続的軸引上げの方が安定成長の面で優れている。
In order to solve this problem, the present inventors have conducted intensive research. As a result, the Pt jig / tool holding the substrate during the growth is pulled up continuously or intermittently, thereby reducing the time for the Pt jig to contact the melt. As a result of the reduction, it was found that the flux mixing into the film can be reduced, and as a result, the generation of cracks during growth and during polishing / etching can be suppressed. As the shaft pulling method, either continuous or intermittent can be adopted, but continuous shaft pulling is superior in terms of stable growth.

　連続的に種結晶基板を引上げる速度Ｖは、２μｍ／ｈｒ以上５０μｍ／ｈｒ以下が好適である。より好ましくは、４μｍ／ｈｒ以上２０μｍ／ｈｒ以下、更に好ましくは、６μｍ／ｈｒ以上１０μｍ／ｈｒ以下である。２μｍ／ｈｒ未満では、軸引上げによるフラックス巻き込み低減効果が少なく、５０μｍ／ｈｒを超えると基板が融液表面より離れる可能性がある。間欠的に種結晶基板を引上げる際は、その平均速度が上記の範囲となることが好ましい。すなわち、間欠的に種結晶基板を引上げる平均速度ｖは、２μｍ／ｈｒ以上５０μｍ／ｈｒ以下が好適であり、より好ましくは、４μｍ／ｈｒ以上２０μｍ／ｈｒ以下、更に好ましくは、６μｍ／ｈｒ以上１０μｍ／ｈｒ以下である。
The speed V for continuously pulling up the seed crystal substrate is preferably 2 μm / hr or more and 50 μm / hr or less. More preferably, it is 4 μm / hr or more and 20 μm / hr or less, and further preferably 6 μm / hr or more and 10 μm / hr or less. If it is less than 2 μm / hr, the effect of reducing the entrainment of flux by pulling up the shaft is small, and if it exceeds 50 μm / hr, the substrate may be separated from the melt surface. When the seed crystal substrate is pulled up intermittently, the average speed is preferably within the above range. That is, the average speed v for intermittently pulling up the seed crystal substrate is preferably 2 μm / hr or more and 50 μm / hr or less, more preferably 4 μm / hr or more and 20 μm / hr or less, and further preferably 6 μm / hr or more. 10 μm / hr or less.

　使用できる溶媒は、溶質であるＺｎＯおよびＭｇＯを融解させることができるものであれば特に制限されないが、ＰｂＯおよびＢｉ２Ｏ３の組み合わせであるか、ＰｂＦ２およびＰｂＯの組み合わせであることが好ましい。上記溶質と、溶媒との混合比は、ＺｎＯのみに換算した溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％が好ましく、より好ましくは、溶質濃度が、５ｍｏｌ％以上１０ｍｏｌ％以下である。溶質濃度が、５ｍｏｌ％未満では成長速度が遅く、１０ｍｏｌ％を超えると成長温度が高くなり、溶媒蒸発量が多くなることがある。
The solvent that can be used is not particularly limited as long as it can melt ZnO and MgO as solutes, but is preferably a combination of PbO and Bi 2 O 3 or a combination of PbF 2 and PbO. The mixing ratio of the solute and the solvent is preferably solute: solvent = 5-30 mol%: 95-70 mol% converted to ZnO alone, and more preferably the solute concentration is 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature increases and the amount of solvent evaporation may increase.

　本発明の好ましい態様では、上記溶質と、溶媒であるＰｂＯおよびＢｉ２Ｏ３との混合比が、ＺｎＯのみに換算した溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％であり、溶媒であるＰｂＯとＢｉ２Ｏ３の混合比がＰｂＯ：Ｂｉ２Ｏ３＝０．１～９５ｍｏｌ％：９９．９～５ｍｏｌ％である。溶媒組成としては、より好ましくは、ＰｂＯ：Ｂｉ２Ｏ３＝３０～９０ｍｏｌ％：７０～１０ｍｏｌ％であり、特に好ましくは、ＰｂＯ：Ｂｉ２Ｏ３＝６０～８０ｍｏｌ％：４０～２０ｍｏｌ％である。ＰｂＯもしくはＢｉ２Ｏ３単独の溶媒では、液相成長温度が高くなるので、上記のような混合比を有するＰｂＯおよびＢｉ２Ｏ３混合溶媒が好適である。ＺｎＯのみに換算した溶質と、溶媒であるＰｂＯおよびＢｉ２Ｏ３との混合比は、より好ましくは、溶質濃度が、５ｍｏｌ％以上１０ｍｏｌ％以下である。溶質濃度が、５ｍｏｌ％未満では成長速度が遅く、１０ｍｏｌ％を超えると成長温度が高くなり、溶媒蒸発量が多くなることがある。
In a preferred embodiment of the present invention, the mixing ratio of the above solute and the solvents PbO and Bi 2 O 3 is solute: solvent = 5-30 mol%: 95-70 mol% converted to ZnO alone, and is a solvent The mixing ratio of PbO and Bi 2 O 3 is PbO: Bi 2 O 3 = 0.1 to 95 mol%: 99.9 to 5 mol%. The solvent composition is more preferably PbO: Bi 2 O 3 = 30 to 90 mol%: 70 to 10 mol%, and particularly preferably PbO: Bi 2 O 3 = 60 to 80 mol%: 40 to 20 mol%. . Since the liquid phase growth temperature becomes high in the solvent of PbO or Bi 2 O 3 alone, the PbO and Bi 2 O 3 mixed solvent having the above mixing ratio is preferable. The mixing ratio of the solute converted to ZnO and the solvents PbO and Bi 2 O 3 is more preferably a solute concentration of 5 mol% or more and 10 mol% or less. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the growth temperature increases and the amount of solvent evaporation may increase.

　本発明の好ましい態様では、上記溶質と、溶媒であるＰｂＦ２およびＰｂＯとの混合比が、ＺｎＯのみに換算した溶質：溶媒＝２～２０ｍｏｌ％：９８～８０ｍｏｌ％であり、溶媒であるＰｂＦ２とＰｂＯの混合比がＰｂＦ２：ＰｂＯ＝８０～２０ｍｏｌ％：２０～８０ｍｏｌ％である。溶媒の混合比が、ＰｂＦ２：ＰｂＯ＝８０～２０ｍｏｌ％：２０～８０ｍｏｌ％であると、溶媒であるＰｂＦ２およびＰｂＯの蒸発量を抑制でき、その結果、溶質濃度の変動が少なくなるので、安定的にＺｎＯ系混晶単結晶を成長させることができる。溶媒であるＰｂＦ２とＰｂＯの混合比は、より好ましくはＰｂＦ２：ＰｂＯ＝６０～４０ｍｏｌ％：４０～６０ｍｏｌ％である。溶質であるＺｎＯおよびＭｇＯと、溶媒であるＰｂＦ２およびＰｂＯとの混合比は、ＺｎＯのみに換算した溶質が５～１０ｍｏｌ％のときより好ましい。溶質濃度が５ｍｏｌ％未満では、成長速度が遅く、１０ｍｏｌ％を超えると、溶質成分を溶解させる温度が高くなり、溶媒蒸発量が多くなることがある。本発明では、液相成長法を用いる。同法は、気相成長法と異なり、真空系を必要とせず、そのため、低コストでＺｎＯ系混晶単結晶を製造することができる上、熱平衡成長であるため、高い結晶性を有するＺｎＯ系混晶単結晶を成長させることができる。また、過飽和度を制御することにより、成長速度を制御でき、比較的高い成長速度を実現できる。
In a preferred embodiment of the present invention, the mixing ratio of the solute and the solvents PbF 2 and PbO is solute converted to ZnO alone: solvent = 2 to 20 mol%: 98 to 80 mol%, and the solvent PbF 2 The mixing ratio of PbO and PbO is PbF 2 : PbO = 80 to 20 mol%: 20 to 80 mol%. When the solvent mixing ratio is PbF 2 : PbO = 80 to 20 mol%: 20 to 80 mol%, the amount of evaporation of the solvents PbF 2 and PbO can be suppressed, and as a result, fluctuations in the solute concentration are reduced. A ZnO mixed crystal single crystal can be stably grown. The mixing ratio of PbF 2 and PbO as the solvent is more preferably PbF 2 : PbO = 60 to 40 mol%: 40 to 60 mol%. The mixing ratio of the solutes ZnO and MgO to the solvents PbF 2 and PbO is more preferable when the solute converted to ZnO alone is 5 to 10 mol%. If the solute concentration is less than 5 mol%, the growth rate is slow, and if it exceeds 10 mol%, the temperature at which the solute component is dissolved increases and the amount of solvent evaporation may increase. In the present invention, a liquid phase growth method is used. Unlike the vapor phase growth method, this method does not require a vacuum system. Therefore, a ZnO mixed crystal single crystal can be manufactured at a low cost, and since it is thermal equilibrium growth, it has a high crystallinity. Mixed crystal single crystals can be grown. Further, by controlling the degree of supersaturation, the growth rate can be controlled, and a relatively high growth rate can be realized.

　本発明の好ましい態様では、上記Ｍｇ含有ＺｎＯ系混晶単結晶が、少量の異種元素を含む。ＺｎＯは、異種元素をドーピングすることでその特性を発現・変化させることができる。本発明の好ましい態様では、Ｌｉ、Ｎａ、Ｋ、Ｃｓ、Ｒｂ、Ｂｅ、Ｃａ、Ｓｒ、Ｂａ、Ｃｕ、Ａｇ、Ｎ、Ｐ、Ａｓ、Ｓｂ、Ｂｉ、Ｂ、Ｔｌ、Ｃｌ、Ｂｒ、Ｉ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｄ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗおよびランタノイド元素等からなる群より選択される１以上を添加する。添加量は、溶質として使用されるＺｎＯに対して２０ｍｏｌ％以下、好ましくは１０ｍｏｌ％以下、より好ましくは１ｍｏｌ％以下である。異種元素を添加することにより、ｐ型半導体、ｎ型半導体、磁性半導体、導電率の制御、バリスタ応用、圧電体応用、電界発光素子および透明ＴＦＴへの応用等がある。
In a preferred embodiment of the present invention, the Mg-containing ZnO mixed single crystal contains a small amount of different elements. ZnO can exhibit and change its characteristics by doping with different elements. In a preferred embodiment of the present invention, Li, Na, K, Cs, Rb, Be, Ca, Sr, Ba, Cu, Ag, N, P, As, Sb, Bi, B, Tl, Cl, Br, I, Mn One or more selected from the group consisting of Fe, Co, Ni, Cd, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and a lanthanoid element are added. The addition amount is 20 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, with respect to ZnO used as a solute. By adding different kinds of elements, there are p-type semiconductors, n-type semiconductors, magnetic semiconductors, conductivity control, varistor applications, piezoelectric body applications, electroluminescent elements, and transparent TFTs.

　本発明の好ましい態様では、成長用基板である種結晶基板としてＺｎＯ単結晶を用いる。ＺｎＯ系混晶成長用基板としては、ＺｎＯと同類の結晶構造を持ち、成長薄膜と基板とが反応しないものであれば使用可能である。例えば、サファイヤ、ＬｉＧａＯ２、ＬｉＡｌＯ２、ＬｉＮｂＯ３、ＬｉＴａＯ３、ＳｃＡｌＭｇＯ４、ＧａＮ、ＺｎＯなどが挙げられる。中でも、本発明における目的単結晶がＺｎＯ系混晶単結晶であることを考慮すると、基板と成長結晶の格子整合度が高いＺｎＯ基板を用いたホモエピタキシャル成長が結晶性、歪みの低減、成長膜の反りの低減および基板からの不純物拡散量低減の面で好ましい。
In a preferred embodiment of the present invention, a ZnO single crystal is used as a seed crystal substrate that is a growth substrate. Any ZnO-based mixed crystal growth substrate can be used as long as it has a crystal structure similar to that of ZnO and does not react with the growth thin film. Examples thereof include sapphire, LiGaO 2 , LiAlO 2 , LiNbO 3 , LiTaO 3 , ScAlMgO 4 , GaN, and ZnO. Among these, considering that the target single crystal in the present invention is a ZnO-based mixed crystal single crystal, homoepitaxial growth using a ZnO substrate having a high degree of lattice matching between the substrate and the grown crystal can reduce crystallinity, distortion, and growth film. This is preferable in terms of reducing warpage and reducing the amount of impurity diffusion from the substrate.

　本発明の好ましい態様では、Ｍｇ含有ＺｎＯ系混晶単結晶の成長方位は＋ｃ面である。
　本発明の好ましい態様では、種結晶基板上にＭｇ含有ＺｎＯ系混晶単結晶を成長させた後、成長に用いた基板を研磨あるいはエッチングで除去することで自立化させることができる。その際、成長基板に近い－ｃ面側を少なくとも１０μｍ、好ましくは２０μｍ以上除去することでＺｎとＭｇの不均一層および基板側からのＬｉ拡散層を除去することが可能となる。基板除去方法としては、研磨あるいはエッチング何れの方法も採用可能であるが、膜厚管理しやすい研削＋研磨が好適である。水熱合成基板上にＭｇ含有ＺｎＯ系混晶単結晶を成長させてもよい。研磨またはエッチング後で５０μｍ程度の膜厚とするためには、成長段階で１００μｍ程度の膜厚が必要となる。成長後、基板側をセラミックスプレートにＷＡＸ固定を行い、研削器にて液相エピタキシャル成長面を平坦化することができる。ＬＰＥ面側（＋ｃ面）セラミックスプレートに張替え、研削器にて基板厚相当を研削除去することで液相エピタキシャル成長膜だけとし、表裏面のうち少なくとも１面をラップおよびポリッシュすることで研磨することができる。このとき、ＬＰＥ成長膜の水熱合成基板側は好ましくは１０μｍ、より好ましくは２０μｍ以上研磨することで水熱合成基板からのＬｉ拡散層を除去することが可能となる。
In a preferred embodiment of the present invention, the growth orientation of the Mg-containing ZnO mixed single crystal is the + c plane.
In a preferred embodiment of the present invention, an Mg-containing ZnO mixed single crystal is grown on a seed crystal substrate, and then the substrate used for the growth can be removed by polishing or etching. At that time, by removing at least 10 μm, preferably 20 μm or more, on the −c plane side close to the growth substrate, it becomes possible to remove the heterogeneous layer of Zn and Mg and the Li diffusion layer from the substrate side. As a substrate removing method, any method of polishing or etching can be adopted, but grinding + polishing which allows easy film thickness management is preferable. An Mg-containing ZnO mixed single crystal may be grown on the hydrothermal synthesis substrate. In order to obtain a film thickness of about 50 μm after polishing or etching, a film thickness of about 100 μm is required at the growth stage. After the growth, the substrate side is fixed to the ceramic plate by WAX, and the liquid phase epitaxial growth surface can be flattened by a grinder. It is possible to polish by lapping and polishing at least one of the front and back surfaces by replacing the LPE surface side (+ c surface) with a ceramic plate and grinding and removing the substrate thickness with a grinder to make only the liquid phase epitaxial growth film. it can. At this time, it is possible to remove the Li diffusion layer from the hydrothermal synthesis substrate by polishing the hydrothermal synthesis substrate side of the LPE growth film preferably at 10 μm, more preferably 20 μm or more.

　本発明の別の実施形態は、上記Ｍｇ含有ＺｎＯ系混晶単結晶の製造方法によってＭｇ含有ＺｎＯ系混晶単結晶を成長させ、これを基板として用い、この基板上に更にＺｎＯ単結晶あるいはＭｇ含有ＺｎＯ系混晶単結晶を成長させることを特徴とするＭｇ含有ＺｎＯ系混晶単結晶積層体の製造方法である。第一成長層と第二成長層のバンドギャップは任意に設定可能であるが、電子素子応用および光学素子応用を考慮すると、第一成長層のバンドギャップ＜第二の成長層のバンドギャップが好ましい。積層体を成長させる方法としては、ＬＰＥ成長を２回行ってもよく、例えば、成長炉内に組成の異なる融液を複数用意し、成長軸を移動させることで積層体を成長させてもよい。あるいは、スライディングボート法を用いて積層体を成長させることもできる。
According to another embodiment of the present invention, an Mg-containing ZnO mixed crystal single crystal is grown by the above-described method for producing an Mg-containing ZnO mixed crystal single crystal, and this is used as a substrate. A method for producing a Mg-containing ZnO mixed crystal single crystal laminate, comprising growing a ZnO-based mixed crystal single crystal. The band gap between the first growth layer and the second growth layer can be set arbitrarily, but considering the application of electronic elements and optical elements, the band gap of the first growth layer is preferably less than the band gap of the second growth layer. . As a method of growing the laminate, LPE growth may be performed twice. For example, a plurality of melts having different compositions may be prepared in a growth furnace, and the laminate may be grown by moving the growth axis. . Alternatively, the laminate can be grown using a sliding boat method.

　本発明における自立Ｍｇ含有ＺｎＯ系混晶単結晶成長法としては、液相エピタキシャル法（ＬＰＥ法）用いる。液相エピタキシャル法によれば、機能別層構造を形成しやすいため、特に、電子素子や光学素子等への応用に有利である。
As the self-standing Mg-containing ZnO mixed single crystal growth method in the present invention, a liquid phase epitaxial method (LPE method) is used. According to the liquid phase epitaxial method, it is easy to form a layer structure classified by function, which is particularly advantageous for application to electronic elements and optical elements.

　本発明の第４の実施形態においては、ＺｎＯおよびＭｇＯ溶解度や溶媒蒸発量、好ましくはＰｂＯおよびＢｉ２Ｏ３蒸発量あるいはＰｂＦ２およびＰｂＯ蒸発量が大きく変化しない範囲で、液相成長温度の制御、溶媒粘性の調整および異種元素ドーピングを目的として、溶媒に第三成分を１種または２種以上添加することができる。例えば、Ｂ２Ｏ３、Ｐ２Ｏ５、Ｖ２Ｏ５、ＭｏＯ３、ＷＯ３、ＳｉＯ２、ＢａＯなどが挙げられる。また、ＰｂＯおよびＰｂＦ２溶媒に、第三成分としてＢｉ２Ｏ３を添加してもよい。
　また、本発明の好ましい態様においては、Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有させることで、電気伝導性を持つＭｇ含有ＺｎＯ系混晶単結晶を液相エピタキシャル成長法で製造できる。
In the fourth embodiment of the present invention, the control of the liquid phase growth temperature is performed so that the solubility of ZnO and MgO and the amount of solvent evaporation, preferably the amount of evaporation of PbO and Bi 2 O 3 or the amount of evaporation of PbF 2 and PbO do not change significantly. For the purpose of adjusting the viscosity of the solvent and doping with different elements, one or more third components can be added to the solvent. For example, B 2 O 3, P 2 O 5, V 2 O 5, MoO 3, WO 3, SiO 2, BaO , and the like. Further, Bi 2 O 3 may be added as a third component to the PbO and PbF 2 solvents.
In a preferred embodiment of the present invention, an Mg-containing ZnO mixed single crystal having electrical conductivity is added to the liquid phase by containing one or more selected from the group consisting of Al, Ga, In, H and F. It can be manufactured by an epitaxial growth method.
　本発明の第５の実施形態は、上記第４の実施形態に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーであって、５０μｍ以上の厚みを有し、膜厚方向、および、面内方向の何れに対しても均一なＺｎとＭｇの化学組成を有し、表裏面のうち少なくとも１面がエピタキシャル成長用基板として利用可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。厚みが５０μｍ未満では取り扱うのが困難となるため好ましくない。厚みの上限は規定されないが、５００μｍを超えると成長時間が長くなる。自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーの膜厚方向、および、面内方向の組成均一性は、好ましくは±１０％以内、更に好ましくは±５％以内である。組成均一性の評価方法は、前述したとおりである。組成均一性が±１０％を超えると近紫外域での透過率が減少するので好ましくない。自立Ｍｇ含有ＺｎＯ混晶単結晶ウエファーの表裏面のうち少なくとも1面の平坦性は、エピタキシャル成長可能な程度であればよい。例えば、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー任意の位置の５０μｍ四方のＲａが０．５ｎｍ以下であることが好ましく、更に好ましくは０．３ｎｍｍ以下である。０．５ｎｍを超えるとＬＥＤ成長膜が３次元成長したり、ピット不良が増える傾向があるので好ましくない。一方、表裏面の平坦性はできるだけ近い方が好ましい。表面と裏面とで平坦性が異なると、反りの発生要因となる。 The fifth embodiment of the present invention is a self-supporting Mg-containing ZnO mixed crystal single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed crystal single crystal described in the fourth embodiment, and is 50 μm or more. And has a uniform chemical composition of Zn and Mg in both the film thickness direction and the in-plane direction, and at least one of the front and back surfaces can be used as a substrate for epitaxial growth. It is a self-supporting Mg-containing ZnO mixed crystal single crystal wafer characterized by having A thickness of less than 50 μm is not preferable because it becomes difficult to handle. The upper limit of the thickness is not specified, but if it exceeds 500 μm, the growth time becomes longer. The composition uniformity in the film thickness direction and in-plane direction of the self-supporting Mg-containing ZnO mixed single crystal wafer is preferably within ± 10%, more preferably within ± 5%. The method for evaluating composition uniformity is as described above. If the composition uniformity exceeds ± 10%, the transmittance in the near ultraviolet region decreases, which is not preferable. The flatness of at least one of the front and back surfaces of the free-standing Mg-containing ZnO mixed crystal single crystal wafer may be such that epitaxial growth is possible. For example, the 50 μm square Ra at an arbitrary position of the free-standing Mg-containing ZnO-based mixed crystal single crystal wafer is preferably 0.5 nm or less, and more preferably 0.3 nm or less. If the thickness exceeds 0.5 nm, the LED growth film tends to grow three-dimensionally or pit defects tend to increase, such being undesirable. On the other hand, the flatness of the front and back surfaces is preferably as close as possible. If the flatness is different between the front surface and the back surface, it causes warping.

　本発明の好ましい実施形態は、バンドギャップ（Ｅｇ）値がウエファーの面内方向、および、厚み方向に対して均一であり、かつ、３．３０ｅＶを超える自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーである。バンドギャップ（Ｅｇ）値の均一性は、前述のとおりＰＬおよびＣＬ発光波長から求めることができる。ＺｎＯ系混晶単結晶のバンドギャップが３．３０ｅＶを下回るようではＭｇＯの混晶化率が低くなる。
A preferred embodiment of the present invention is a self-standing Mg-containing ZnO mixed single crystal wafer having a band gap (Eg) value that is uniform in the in-plane direction and the thickness direction of the wafer and exceeds 3.30 eV. is there. The uniformity of the band gap (Eg) value can be obtained from the PL and CL emission wavelengths as described above. If the band gap of the ZnO-based mixed crystal single crystal is less than 3.30 eV, the mixed crystal ratio of MgO is lowered.

　本発明の好ましい態様では、第４の実施形態に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーは、Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有する。Ａｌ、Ｇａ、Ｉｎ、ＨおよびＦからなる群より選択される１以上を含有することにより、電気伝導性を発現することが可能となる。研磨やエッチング等により成長で用いた基板を除去すれば、電子素子や光学素子の表裏面に電極を形成することができる。従って、自立化した導電性があるＭｇ含有ＺｎＯ系混晶単結晶を提供できることになる。このように導電性を有する自立Ｍｇ含有ＺｎＯ系混晶単結晶は、ＺｎＯ－ＬＥＤデバイスにおいてＬＥＤ光に透明で、格子整合し、導電性を持つ基板とすることができる。
In a preferred aspect of the present invention, the self-supporting Mg-containing ZnO mixed crystal single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment includes Al, Ga, In, H and 1 or more selected from the group consisting of F. By containing one or more selected from the group consisting of Al, Ga, In, H, and F, it becomes possible to develop electrical conductivity. If the substrate used for growth is removed by polishing, etching, or the like, electrodes can be formed on the front and back surfaces of the electronic element or optical element. Accordingly, it is possible to provide a Mg-containing ZnO mixed single crystal having self-supporting conductivity. Thus, the self-supporting Mg-containing ZnO mixed single crystal having conductivity is transparent to LED light in a ZnO-LED device, and can be a lattice-matched substrate having conductivity.

　本発明の好ましい態様では、第４の実施形態に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーは、Ｌｉ濃度が、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、好ましくは１×１０１５個／ｃｍ３以下、更に好ましくは１×１０１４個／ｃｍ３以下である。ここで、Ｌｉ濃度が１×１０１５個／ｃｍ３以下で均一であるとは、デバイス動作を不安定化するＬｉ濃度が自立化膜全体で１×１０１５個／ｃｍ３以下であることを意味する。Ｌｉ濃度の均一性は、前述した方法で評価することができる。
In a preferred aspect of the present invention, the self-standing Mg-containing ZnO mixed single crystal wafer obtained by the method for producing an Mg-containing ZnO mixed single crystal described in the fourth embodiment has an Li concentration in the plane of the wafer. direction, and a uniform relative thickness direction, and preferably 1 × 10 15 atoms / cm 3 or less, further preferably 1 × 10 14 atoms / cm 3 or less. Here, when the Li concentration is uniform at 1 × 10 15 pieces / cm 3 or less, the Li concentration that destabilizes the device operation is 1 × 10 15 pieces / cm 3 or less in the entire self-supporting film. means. The uniformity of the Li concentration can be evaluated by the method described above.

　以下、本発明の一実施態様に係わるＺｎＯ単結晶の育成法として、ＺｎＯ基板上にIII族元素をドープしたＺｎＯ単結晶を液相エピタキシャル（ＬＰＥ）成長法によって成長させる方法について説明する。本発明は、以下の実施例に何ら限定されるものではない。
Hereinafter, as a method for growing a ZnO single crystal according to an embodiment of the present invention, a method for growing a ZnO single crystal doped with a group III element on a ZnO substrate by a liquid phase epitaxial (LPE) growth method will be described. The present invention is not limited to the following examples.

　ここで用いた炉の構成図を図４に示す。
　単結晶製造炉内には、原料を溶融し融液として収容する白金るつぼ４が、るつぼ台９の上に設けられている。白金るつぼ４の外側にあって側方には、白金るつぼ４内の原料を加熱して溶融する３段の側部ヒーター（上段ヒーター１、中央部ヒーター２、下段ヒーター３）が設けられている。ヒーターは、それらの出力が独立に制御され、融液に対する加熱量が独立して調整される。ヒーターと製造炉の内壁との間には、炉心管１１が設けられ、炉心管１１の上部には炉内の開閉を行う炉蓋１２が設けられている。白金るつぼ４の上方には引上げ機構が設けられている。引上げ機構には引上軸５が固定され、その先端には、基板ホルダー６とホルダーで固定された基板７が設けられている。引上軸５上部には、引上軸５を回転させる機構が設けられている。白金るつぼ４の下方には、るつぼの温度を管理するための熱電対１０が設けられている。成長炉を構成する部材については、非Ａｌ系が好適である。非Ａｌ系炉材としては、ＺｎＯ炉材が最適であるが、市販されていないことを考慮すると、ＺｎＯ薄膜に混入してもキャリヤとして働かない材料としてＭｇＯが好適である。また、アルミナ＋シリカで構成されるムライト製炉材を使用してもＬＰＥ膜中のＳｉ不純物濃度が増えないＳＩＭＳ分析結果を考慮すると、石英炉材も好適である。その他には、カルシヤ、シリカ、ＺｒＯ２およびジルコン（ＺｒＯ２＋ＳｉＯ２）、ＳｉＣ、Ｓｉ３Ｎ４等も利用可能である。
A configuration diagram of the furnace used here is shown in FIG.
In the single crystal manufacturing furnace, a platinum crucible 4 for melting a raw material and storing it as a melt is provided on a crucible base 9. Outside the platinum crucible 4 and on the side thereof, three-stage side heaters (upper heater 1, central heater 2, lower heater 3) for heating and melting the raw material in the platinum crucible 4 are provided. . The outputs of the heaters are controlled independently, and the heating amount for the melt is adjusted independently. A core tube 11 is provided between the heater and the inner wall of the manufacturing furnace, and a furnace lid 12 for opening and closing the inside of the furnace is provided above the core tube 11. A pulling mechanism is provided above the platinum crucible 4. A pulling-up shaft 5 is fixed to the pulling mechanism, and a substrate holder 6 and a substrate 7 fixed by the holder are provided at the tip thereof. A mechanism for rotating the pull-up shaft 5 is provided on the pull-up shaft 5. Below the platinum crucible 4, a thermocouple 10 for managing the temperature of the crucible is provided. The non-Al system is suitable for the members constituting the growth furnace. As a non-Al-based furnace material, a ZnO furnace material is optimal, but considering that it is not commercially available, MgO is suitable as a material that does not function as a carrier even when mixed in a ZnO thin film. In view of SIMS analysis results in which the Si impurity concentration in the LPE film does not increase even when a mullite furnace material composed of alumina + silica is used, a quartz furnace material is also preferable. In addition, calcium, silica, ZrO 2 and zircon (ZrO 2 + SiO 2 ), SiC, Si 3 N 4 and the like can be used.

　以上より、非Ａｌ系の炉材としてＭｇＯおよび／または石英から構成される成長炉を用いてIII族元素をドープしたＺｎＯ単結晶およびＭｇ含有ＺｎＯ系混晶単結晶（Ｚｎ１－ｘＭｇｘＯの組成で表される）を成長させることが好ましい。更に、成長炉が、るつぼを載置するためのるつぼ台、該るつぼ台の外周を取り囲むように設けられた炉心管、該炉心管の上部に設けられ、炉内の開閉を行う炉蓋、及び種結晶または基板を上下させるための引上軸が、それぞれ独立に、ＭｇＯまたは石英によって作製されているものが好ましく使用される。
As described above, a ZnO single crystal doped with a group III element and a Mg-containing ZnO mixed crystal single crystal (Zn 1-x Mg x O) using a growth furnace composed of MgO and / or quartz as a non-Al furnace material. It is preferred to grow A growth furnace having a crucible for placing the crucible; a core tube provided to surround the outer periphery of the crucible base; a furnace lid provided at an upper portion of the core tube for opening and closing the furnace; and Preferably, the pulling shaft for moving the seed crystal or the substrate up and down is independently made of MgO or quartz.

　白金るつぼ内の原料を溶融するため、原料が溶融するまで製造炉を昇温する。好ましくは８００～１１００℃まで昇温し、２～３時間静置して原料融液を安定化させる。Ｐｔ製攪拌羽根で攪拌することで、静置時間を短縮してもよい。このとき、３段ヒーターにオフセットを掛け、融液表面よりるつぼ底が数度高くなるよう調節する。好ましくは、－１００℃≦Ｈ１オフセット≦０℃、０℃≦Ｈ３オフセット≦１００℃、さらに好ましくは、－５０℃≦Ｈ１オフセット≦０℃、０℃≦Ｈ３オフセット≦５０℃である。るつぼ底温度が７００～９５０℃の種付け温度になるよう調節し、融液の温度が安定化した後、基板を５～１２０ｒｐｍで回転させながら、引上軸を下降させることで基板を融液表面に接液する。基板を融液になじませた後、温度一定または、０．０１～３．０℃／ｈｒで温度降下を開始し、基板面に目的とするＺｎＯ単結晶あるいはＭｇ含有ＺｎＯ系混晶単結晶を成長させる。成長時も基板は引上軸の回転によって５～３００ｒｐｍで回転しており、一定時間間隔ごとに逆回転させる。３０分から１００時間程度結晶成長させた後、基板を融液から切り離し、引上軸を２００～３００ｒｐｍ程度の高速で回転させることで、融液成分を分離させる。その後、室温まで１～２４時間かけて冷却して目的のＺｎＯ単結晶あるいはＭｇ含有ＺｎＯ系混晶単結晶を得る。
In order to melt the raw material in the platinum crucible, the temperature of the production furnace is increased until the raw material is melted. Preferably, the temperature is raised to 800 to 1100 ° C. and left for 2 to 3 hours to stabilize the raw material melt. The standing time may be shortened by stirring with a Pt stirring blade. At this time, an offset is applied to the three-stage heater, and the bottom of the crucible is adjusted to be several degrees higher than the melt surface. Preferably, −100 ° C. ≦ H1 offset ≦ 0 ° C., 0 ° C. ≦ H3 offset ≦ 100 ° C., and more preferably −50 ° C. ≦ H1 offset ≦ 0 ° C., 0 ° C. ≦ H3 offset ≦ 50 ° C. After the bottom temperature of the crucible is adjusted to a seeding temperature of 700 to 950 ° C and the melt temperature is stabilized, the substrate is brought to the melt surface by lowering the pulling shaft while rotating the substrate at 5 to 120 rpm. Wetted in contact with. After allowing the substrate to adjust to the melt, the temperature starts to decrease at a constant temperature or from 0.01 to 3.0 ° C./hr, and the target ZnO single crystal or Mg-containing ZnO mixed single crystal is formed on the substrate surface. Grow. Even during growth, the substrate is rotated at 5 to 300 rpm by the rotation of the pulling shaft, and is rotated reversely at regular time intervals. After crystal growth for about 30 minutes to 100 hours, the substrate is separated from the melt, and the melt component is separated by rotating the pulling shaft at a high speed of about 200 to 300 rpm. Thereafter, the target ZnO single crystal or Mg-containing ZnO mixed single crystal is obtained by cooling to room temperature over 1 to 24 hours.

（実施例１）
以下の工程により、ＺｎＯ単結晶を液相エピタキシャル成長法で作製した。内径７５ｍｍΦ、高さ７５ｍｍｈ、厚さ１ｍｍの白金るつぼに、原料としてＺｎＯ、ＰｂＯ、およびＢｉ２Ｏ３をそれぞれ、３３．２０ｇ、８２９．５３ｇおよび７９４．７５ｇ仕込んだ。このときの溶質であるＺｎＯの濃度は７ｍｏｌ％で、溶媒であるＰｂＯおよびＢｉ２Ｏ３の濃度は、ＰｂＯ：Ｂｉ２Ｏ３＝６８．５ｍｏｌ％：３１．５ｍｏｌ％となる。原料を仕込んだるつぼを図４に示す炉に設置し、るつぼ底温度約８４０℃で１時間保持しＰｔ攪拌冶具で攪拌し溶解させた。その後、るつぼ底温度が約７９０℃になるまで降温してから、水熱合成法で育成した＋ｃ面方位でサイズが１０ｍｍ×１０ｍｍ×０．５ｍｍｔのＺｎＯ単結晶基板を種結晶として接液し、引上軸を３０ｒｐｍで回転させながら同温度で８０時間成長させた。また、Ｈ１、Ｈ２、Ｈ３の設定温度は、オフセット差を維持したまま、－０．１℃／ｈｒの速度で降温させた。また、ＬＰＥ成長の間、すなわち８０時間かけて引上げ軸を連続的に５００μｍ程度引上げた。このときの軸引上げ速度は約６．３μｍ／ｈｒとなる。また、このとき軸回転方向は２分おきに反転させた。その後、引上軸を上昇させることで、融液から切り離し、１００ｒｐｍで軸を回転させることで、融液成分を振り切り、その後室温まで徐冷して無色透明のＺｎＯ単結晶を得た。室温まで冷却後成長膜をＬＰＥ炉から取出しＰｔ治工具周辺を観察したがフラックス析出は見られなかった。ＬＰＥ成長膜厚は３９１μｍで、このときの成長速度は、約４．９μｍ／ｈｒであった。続いて、以下に示す自立化処理を施した。裏面（水熱合成基板の－ｃ面側）を、セラミックスプレートにＷＡＸで固定した。横型平面研削盤で＋ｃ面のＬＰＥ面が平坦になるよう約５０μｍ研削処理した。その後、表裏を張替え、水熱合成基板の厚みに相当する量を研削処理することで自立ＺｎＯ単結晶を得た。厚みは約３４１μｍ程度であった。自立膜をセラミックスプレートに再度ＷＡＸ固定し、ダイヤモンドスラリーでラップ処理を、コロイダルシリカでポリッシュ処理を施した。自立膜の表裏の研磨量は、＋ｃ面で３３μｍ、－ｃ面で２８μｍであり、結果厚さ約２８０μｍの自立ＺｎＯ単結晶を得た。研削、研磨の過程でクラックの発生はなかった。自立化処理後、±ｃ面をダイナミックＳＩＭＳで分析し、Ｌｉ濃度を求めた。±ｃ面ともＬｉ濃度は検出下限である５×１０１３個／ｃｍ３以下であった。なお、本明細書において、ダイナミックＳＩＭＳ分析は、Ｃａｍｅｃａ製装置を用いて、一次イオン種；Ｏ２＋、一次イオン加速電圧；８ＫｅＶ、測定温度；室温の条件下で行う。また、同膜をｃ面に垂直の方向で切断し、切断面をＳＩＭＳ分析したところ、Ｌｉ濃度は検出下限以下の５×１０１３個／ｃｍ３であった。自立膜の結晶性を示す（００２）面のロッキングカーブ半値幅は約３３ａｒｃｓｅｃで結晶性が高いことを示している。伝導性を示すキャリヤ濃度は２．０×１０１７個／ｃｍ３、キャリヤ移動度は１６５ｃｍ２／Ｖ・ｓｅｃとなった。キャリヤ移動度の高さからも品質が高いことを示している。自立膜中央部５０μｍ四方について原子間力顕微鏡（Atomic Force Microscopy：ＡＦＭ）で平坦性を評価したところ、Ｒａ＝０．３ｎｍであった。
Example 1
A ZnO single crystal was produced by a liquid phase epitaxial growth method through the following steps. A platinum crucible having an inner diameter of 75 mmΦ, a height of 75 mmh, and a thickness of 1 mm was charged with 33.20 g, 829.53 g, and 794.75 g of ZnO, PbO, and Bi 2 O 3 as raw materials, respectively. At this time, the concentration of ZnO as a solute is 7 mol%, and the concentrations of PbO and Bi 2 O 3 as solvents are PbO: Bi 2 O 3 = 68.5 mol%: 31.5 mol%. The crucible charged with the raw material was placed in the furnace shown in FIG. 4, held at a crucible bottom temperature of about 840 ° C. for 1 hour, and stirred and melted with a Pt stirring jig. Thereafter, the temperature is lowered until the bottom temperature of the crucible reaches about 790 ° C., and then contacted with a ZnO single crystal substrate having a size of 10 mm × 10 mm × 0.5 mmt grown in a hydrothermal synthesis method as a seed crystal in a + c plane orientation, Growth was performed at the same temperature for 80 hours while rotating the pulling shaft at 30 rpm. The set temperatures of H1, H2, and H3 were decreased at a rate of −0.1 ° C./hr while maintaining the offset difference. Further, during the LPE growth, that is, over 80 hours, the pulling axis was continuously pulled up by about 500 μm. The shaft pulling speed at this time is about 6.3 μm / hr. At this time, the shaft rotation direction was reversed every two minutes. Thereafter, the pulling-up shaft was raised to separate it from the melt, and the shaft was rotated at 100 rpm to shake off the melt components and then gradually cooled to room temperature to obtain a colorless and transparent ZnO single crystal. After cooling to room temperature, the grown film was taken out from the LPE furnace and observed around the Pt jig, but no flux deposition was observed. The LPE growth film thickness was 391 μm, and the growth rate at this time was about 4.9 μm / hr. Subsequently, the following independence treatment was performed. The back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX. About 50 μm was ground so that the + c plane LPE surface was flattened by a horizontal surface grinder. Then, the self-supporting ZnO single crystal was obtained by reversing the front and back and grinding the amount corresponding to the thickness of the hydrothermal synthetic substrate. The thickness was about 341 μm. The self-supporting film was fixed to the ceramic plate again by WAX, lapped with diamond slurry, and polished with colloidal silica. The polishing amount of the front and back surfaces of the free-standing film was 33 μm on the + c surface and 28 μm on the −c surface, and as a result, a free-standing ZnO single crystal having a thickness of about 280 μm was obtained. There were no cracks in the grinding and polishing process. After the self-supporting treatment, the ± c plane was analyzed by dynamic SIMS to determine the Li concentration. The Li concentration was 5 × 10 13 pieces / cm 3 or less, which is the lower limit of detection, on both the ± c planes. In this specification, the dynamic SIMS analysis is performed under the conditions of primary ion species; O 2+ , primary ion acceleration voltage; 8 KeV, measurement temperature; Further, the film was cut in a direction perpendicular to the c-plane, and the cut surface was subjected to SIMS analysis. As a result, the Li concentration was 5 × 10 13 pieces / cm 3 below the detection lower limit. The rocking curve half-value width of the (002) plane showing the crystallinity of the free-standing film is about 33 arcsec, indicating that the crystallinity is high. The carrier concentration exhibiting conductivity was 2.0 × 10 17 particles / cm 3 and the carrier mobility was 165 cm 2 / V · sec. It shows that the quality is high also from the high carrier mobility. When flatness was evaluated with an atomic force microscope (AFM) for the 50 μm square of the center of the free-standing film, Ra = 0.3 nm.

（実施例２－１０および比較例１）
　Ｇａ２Ｏ３をＰｔるつぼに仕込むこと以外、実施例１と同様の方法で自立ＺｎＯ単結晶を得た。実施例１０では、連続的な軸引き上げを間欠的な軸引き上げに変更した。すなわち、軸を停止させて１６時間経過後に１００μｍ引上げる工程を５回繰り返し、８０時間で合計５００μｍ引上げた。仕込み組成を表１に示す。得られた自立膜の物性を表２に示す。
(Example 2-10 and Comparative Example 1)
A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that Ga 2 O 3 was charged into a Pt crucible. In Example 10, continuous shaft pulling was changed to intermittent shaft pulling. That is, the process of stopping the shaft and raising 100 μm after 16 hours was repeated 5 times, and the total was raised by 500 μm in 80 hours. The charge composition is shown in Table 1. Table 2 shows the physical properties of the obtained free-standing film.
　Ｇａ２Ｏ３の仕込み量が増えるに従い、キャリヤ濃度が増加しＺｎＯに対し２１００ｐｐｍ仕込んだ実施例９の自立化膜ではキャリヤ濃度は１．０×１０１９個／ｃｍ３となった。これらの結果から、Ｇａ２Ｏ３を仕込むことでキャリヤ濃度を２．０×１０１７個／ｃｍ３から１．０×１０１９個／ｃｍ３まで制御できることを示している。一方、キャリヤ移動度はＧａ２Ｏ３を仕込まない実施例１では１５４ｃｍ２／Ｖ・ｓｅｃ、２１００ｐｐｍ仕込んだ実施例９では６４ｃｍ２／Ｖ・ｓｅｃとなった。これは、異物であるＧａがドープされた結果と思われる。結晶性を示す（００２）面のロッキングカーブ半値幅は、Ｇａ２Ｏ３の仕込０から２１００ｐｐｍの間で２３から７１ａｒｃｓｅｃとなり極めて結晶性が高いことを示している。また、実施例１－１０では、水熱合成基板側の成長面である－ｃ面部を１２－２９μｍ研磨除去しており、その結果、±ｃ面ともＬｉ濃度はＳＩＭＳ検出下限である５×１０１３個／ｃｍ３以下となった。 As the amount of Ga 2 O 3 charged increased, the carrier concentration increased and the carrier concentration of the self-supporting film of Example 9 charged with 2100 ppm with respect to ZnO was 1.0 × 10 19 atoms / cm 3 . These results indicate that the carrier concentration can be controlled from 2.0 × 10 17 atoms / cm 3 to 1.0 × 10 19 atoms / cm 3 by charging Ga 2 O 3 . On the other hand, the carrier mobility was 154 cm 2 / V · sec in Example 1 in which Ga 2 O 3 was not charged, and 64 cm 2 / V · sec in Example 9 in which 2100 ppm was charged. This seems to be a result of doping Ga, which is a foreign material. The rocking curve half width of the (002) plane showing crystallinity is 23 to 71 arcsec between 0 to 2100 ppm of Ga 2 O 3 , indicating that the crystallinity is extremely high. Further, in Example 1-10, the −c surface portion which is the growth surface on the hydrothermal synthesis substrate side is polished and removed by 12-29 μm. As a result, the Li concentration is 5 × 10 5 which is the SIMS detection lower limit for both ± c surfaces. It was 13 pieces / cm 3 or less.

　また、軸引上げを行わなかった比較例１では、Ｐｔ冶工具近傍にフラックスの析出が観察された。成長膜をＰｔ冶工具から外す際、冶工具を基点としたクラックが発生した。割れた断片の内最も大きい５ｍｍ角相当を用いて自立化処理を施したところ、物性面では実施例９と比較例１では大差がなかった。軸引上げ機構のみ異なる実施例９と１０を比較すると、軸引上げが間欠的である実施例１０の方が結晶性は低下し、キャリヤ移動度が減少している。軸引上げが間欠的であったため、安定的なＬＰＥ成長となっていないことが要因と思われる。
Further, in Comparative Example 1 in which the shaft was not pulled up, flux precipitation was observed in the vicinity of the Pt jig / tool. When the growth film was removed from the Pt jig / tool, a crack with the jig / tool as a base point occurred. When the self-supporting treatment was performed using the largest 5 mm square of the cracked fragments, there was no significant difference between Example 9 and Comparative Example 1 in terms of physical properties. Comparing the ninth and tenth embodiments, which differ only in the shaft pulling mechanism, the crystallinity is lowered and the carrier mobility is decreased in the tenth embodiment in which the shaft pulling is intermittent. The reason is that stable LPE growth has not been achieved because the shaft pulling was intermittent.

　以上の結果から、連続的または間欠的に軸を引上げながらＬＰＥ成長を行うと、Ｐｔ冶工具を基点としたフラックス析出が抑制され、その結果、成長や自立化の過程でのクラックの発生が低減できることを示している。また、ＬＰＥ成長後、成長に用いた基板を研磨で除去し、ＬＰＥ成長膜の水熱合成基板側の－ｃ面を少なくとも１０μｍ以上研磨すれば、ＬＰＥ膜中のＬｉ濃度を１×１０１５個／ｃｍ３以下にすることが可能となる。一方、Ｇａ２Ｏ３の仕込み量を制御することで、自立ＺｎＯ単結晶ウエファーのキャリヤ濃度を２．７×１０１７個／ｃｍ３から１×１０１９個／ｃｍ３程度まで制御できるため、同自立化膜を基板として光学素子や電子素子を構成した場合、自立導電性基板となり、デバイス製造コストや寿命の面で絶縁性基板より有利となる。
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
From the above results, when LPE growth is performed while pulling the shaft continuously or intermittently, flux precipitation based on the Pt jig tool is suppressed, and as a result, the generation of cracks in the process of growth and independence is reduced. It shows what you can do. Further, after the LPE growth, the substrate used for the growth is removed by polishing, and if the −c surface on the hydrothermal synthesis substrate side of the LPE growth film is polished by at least 10 μm or more, the Li concentration in the LPE film is 1 × 10 15 pieces. / Cm 3 or less. On the other hand, since the carrier concentration of the free-standing ZnO single crystal wafer can be controlled from about 2.7 × 10 17 pieces / cm 3 to about 1 × 10 19 pieces / cm 3 by controlling the amount of Ga 2 O 3 charged. When an optical element or an electronic element is configured using a self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
（実施例１１－１８および比較例２）

Ａｌ２Ｏ３をＰｔるつぼに仕込み、表３に示す仕込み組成とする以外、実施例１と同様の方法で自立ＺｎＯ単結晶を得た。実施例１８では、連続的な軸引き上げを間欠的な軸引き上げに変更した。すなわち、軸を停止させて１６時間経過後に１００μｍ引上げる工程を５回繰り返し、８０時間で合計５００μｍ引上げた。得られた自立膜の物性を表４に示す。Ａｌ２Ｏ３仕込量が増えるに従い、キャリヤ濃度が増加しＺｎＯに対し２２００ｐｐｍ仕込んだ実施例１７の自立化膜ではキャリヤ濃度は１．０×１０１９個／ｃｍ３となった。これらの結果から、Ａｌ２Ｏ３を仕込むことでキャリヤ濃度を２．０×１０１７個／ｃｍ３から１．２×１０１９個／ｃｍ３まで制御できることを示している。一方、キャリヤ移動度はＡｌ２Ｏ３を仕込まない実施例１１では１６３ｃｍ２／Ｖ・ｓｅｃ、Ａｌ２Ｏ３を２２００ｐｐｍ仕込んだ実施例１５では９５ｃｍ２／Ｖ・ｓｅｃとなった。これは、異物であるＡｌがドープされた結果と思われる。結晶性を示す（００２）面のロッキングカーブ半値幅は、Ａｌ２Ｏ３の仕込み０から２１７９ｐｐｍの間で１９から５２ａｒｃｓｅｃとなり極めて結晶性が高いことを示している。また、実施例１２－１７では、水熱合成基板側の成長面である－ｃ面部を１３－２４μｍ研磨除去しており、その結果、±ｃ面ともＬｉ濃度はＳＩＭＳ検出下限である５×１０１３個／ｃｍ３以下となった。 (Examples 11-18 and Comparative Example 2)

A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that Al 2 O 3 was charged into a Pt crucible and the charging composition shown in Table 3 was used. In Example 18, continuous shaft pulling was changed to intermittent shaft pulling. That is, the process of stopping the shaft and raising 100 μm after 16 hours was repeated 5 times, and the total was raised by 500 μm in 80 hours. Table 4 shows the physical properties of the obtained self-supporting film. As the Al 2 O 3 charge increased, the carrier concentration increased and the carrier concentration of the self-supporting film of Example 17 charged with 2200 ppm with respect to ZnO was 1.0 × 10 19 particles / cm 3 . From these results, it is shown that the carrier concentration can be controlled from 2.0 × 10 17 pieces / cm 3 to 1.2 × 10 19 pieces / cm 3 by charging Al 2 O 3 . On the other hand, the carrier mobility was the Al 2 O 3 in Example 11 without charged to 163cm 2 / V · sec, the Al 2 O 3 Example 15 was charged 2200ppm of 95cm 2 / V · sec. This is considered to be a result of doping Al as a foreign material. The rocking curve half width of the (002) plane showing crystallinity is 19 to 52 arcsec between 0 to 2179 ppm of Al 2 O 3 , indicating that the crystallinity is extremely high. Further, in Example 12-17, the −c surface portion, which is the growth surface on the hydrothermal synthesis substrate side, is polished and removed by 13-24 μm. It became 13 pieces / cm 3 or less.

　軸引上げを行わなかった比較例２では、Ｐｔ冶工具近傍にフラックスの析出が観察された。成長膜をＰｔ冶工具から外す際、冶工具を基点としたクラックが発生した。割れた断片の内最も大きい５ｍｍ角相当を用いて自立化処理を施したところ、物性面では実施例１７と比較例２では大差がなかった。軸引上げ機構のみ異なる実施例１７と１８を比較すると、軸引上げが間欠的である実施例１８の方が結晶性は低下し、キャリヤ移動度が減少している。軸引上げが間欠的であったため、安定的なＬＰＥ成長となっていないことが要因と思われる。
In Comparative Example 2 in which the shaft was not pulled up, flux precipitation was observed in the vicinity of the Pt jig / tool. When the growth film was removed from the Pt jig / tool, a crack with the jig / tool as a base point occurred. When the self-supporting treatment was performed using the largest 5 mm square of the cracked fragments, there was no significant difference between Example 17 and Comparative Example 2 in terms of physical properties. Comparing Examples 17 and 18 that differ only in the shaft pulling mechanism, the crystallinity is lowered and carrier mobility is decreased in Example 18 in which the shaft pulling is intermittent. The reason is that stable LPE growth has not been achieved because the shaft pulling was intermittent.

　以上の結果から、連続的または間欠的に軸を引上げながらＬＰＥ成長を行うと、Ｐｔ冶工具を基点としたフラックス析出が抑制され、その結果、成長や自立化の過程でのクラックの発生が低減できることを示している。また、ＬＰＥ成長後、成長に用いた基板を研磨で除去し、ＬＰＥ成長膜の水熱合成基板側の－ｃ面を少なくとも１０μｍ以上研磨すれば、ＬＰＥ膜中のＬｉ濃度を１×１０１５個／ｃｍ３以下にすることが可能となる。一方、Ａｌ２Ｏ３の仕込み量を制御することで、自立ＺｎＯ単結晶ウエファーのキャリヤ濃度を２．０×１０１７個／ｃｍ３から１×１０１９個／ｃｍ３程度まで制御できるため、同自立化膜を基板として光学素子や電子素子を構成した場合、自立導電性基板となり、デバイス製造コストや寿命の面で絶縁性基板より有利となる。
Figure JPOXMLDOC01-appb-T000003
From the above results, when LPE growth is performed while pulling the shaft continuously or intermittently, flux precipitation based on the Pt jig tool is suppressed, and as a result, the generation of cracks in the process of growth and independence is reduced. It shows what you can do. Further, after the LPE growth, the substrate used for the growth is removed by polishing, and if the −c surface on the hydrothermal synthesis substrate side of the LPE growth film is polished by at least 10 μm or more, the Li concentration in the LPE film is 1 × 10 15 pieces. / Cm 3 or less. On the other hand, the carrier concentration of the free-standing ZnO single crystal wafer can be controlled from 2.0 × 10 17 pieces / cm 3 to about 1 × 10 19 pieces / cm 3 by controlling the amount of Al 2 O 3 charged. When an optical element or an electronic element is configured using a self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
 （実施例１９－２２）

Ｉｎ２Ｏ３をＰｔるつぼに仕込み、表５に示す仕込み組成とした以外、実施例１と同様の方法で自立ＺｎＯ単結晶を得た。得られた自立膜の物性を表６に示す。Ｉｎ２Ｏ３仕込み量が増えるに従い、キャリヤ濃度が増加しＺｎＯに対し１４０ｐｐｍ仕込んだ実施例２２の自立化膜ではキャリヤ濃度は３．５×１０１７個／ｃｍ３となった。これらの結果から、Ｉｎ２Ｏ３を仕込むことでキャリヤ濃度を２．０×１０１７個／ｃｍ３から３．５×１０１７個／ｃｍ３まで制御できることを示している。一方、キャリヤ移動度はＩｎ２Ｏ３を仕込まない実施例１９では１６８ｃｍ２／Ｖ・ｓｅｃ、１４０ｐｐｍ仕込んだ実施例２２では１３４ｃｍ２／Ｖ・ｓｅｃとなった。これは、異物であるＩｎがドープされた結果と思われる。結晶性を示す（００２）面のロッキングカーブ半値幅は、Ｉｎ２Ｏ３の仕込み０から１４０ｐｐｍの間で１９から５８ａｒｃｓｅｃとなり極めて結晶性が高いことを示している。また、実施例１９－２２では、水熱合成基板側の成長面である－ｃ面部を１９－２４μｍ研磨除去しており、その結果、±ｃ面ともＬｉ濃度はＳＩＭＳ検出下限である５×１０１３個／ｃｍ３以下となった。
Figure JPOXMLDOC01-appb-T000004
 Examples 19-22

A self-supporting ZnO single crystal was obtained in the same manner as in Example 1 except that In 2 O 3 was charged into a Pt crucible and the charging composition shown in Table 5 was adopted. Table 6 shows the physical properties of the obtained self-supporting film. As the amount of In 2 O 3 charged increased, the carrier concentration increased and the carrier concentration of the self-supporting film of Example 22 charged with 140 ppm with respect to ZnO was 3.5 × 10 17 particles / cm 3 . From these results, it is shown that the carrier concentration can be controlled from 2.0 × 10 17 pieces / cm 3 to 3.5 × 10 17 pieces / cm 3 by charging In 2 O 3 . On the other hand, the carrier mobility was 168 cm 2 / V · sec in Example 19 in which In 2 O 3 was not charged, and 134 cm 2 / V · sec in Example 22 in which 140 ppm was charged. This is considered to be a result of doping In which is a foreign substance. The rocking curve half width of the (002) plane showing crystallinity is 19 to 58 arcsec between 0 to 140 ppm of In 2 O 3 , indicating that the crystallinity is extremely high. In Example 19-22, the −c surface portion, which is the growth surface on the hydrothermal synthesis substrate side, was polished and removed by 19-24 μm. It became 13 pieces / cm 3 or less.

　以上の結果から、連続的に軸を引上げながらＬＰＥ成長を行うと、Ｐｔ冶工具を基点としたフラックス析出が抑制され、その結果、成長や自立化の過程でのクラックの発生が低減できることを示している。また、ＬＰＥ成長後、成長に用いた基板を研磨で除去し、ＬＰＥ成長膜の水熱合成基板側の－ｃ面を少なくとも１０μｍ以上研磨すれば、ＬＰＥ膜中のＬｉ濃度を１×１０１５以下にすることが可能となる。一方、Ｉｎ２Ｏ３の仕込み量を制御することで、自立ＺｎＯ単結晶ウエファーのキャリヤ濃度を２．０×１０１７個／ｃｍ３から３．５×１０１７個／ｃｍ３程度まで制御できるため、同自立化膜を基板として光学素子や電子素子を構成した場合、自立導電性基板となり、デバイス製造コストや寿命の面で絶縁性基板より有利となる。
Figure JPOXMLDOC01-appb-T000005
From the above results, it is shown that when LPE growth is performed while pulling the shaft continuously, flux precipitation based on the Pt jig tool is suppressed, and as a result, the generation of cracks in the process of growth and independence can be reduced. ing. Further, after the LPE growth, the substrate used for the growth is removed by polishing, and if the −c surface on the hydrothermal synthesis substrate side of the LPE growth film is polished at least 10 μm or more, the Li concentration in the LPE film is 1 × 10 15 or less. It becomes possible to. On the other hand, since the carrier concentration of the freestanding ZnO single crystal wafer can be controlled from 2.0 × 10 17 pieces / cm 3 to about 3.5 × 10 17 pieces / cm 3 by controlling the amount of In 2 O 3 charged. When an optical element or an electronic element is configured using the self-supporting film as a substrate, it becomes a self-supporting conductive substrate, which is more advantageous than an insulating substrate in terms of device manufacturing cost and life.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
 （実施例２３）

以下の工程により、ＺｎＯ単結晶を液相エピタキシャル成長法（Ｌｉｑｕｉｄ　ｐｈａｓｅ　ｅｐｉｔａｘｉａｌ）で作製した。内径７５ｍｍΦ、高さ７５ｍｍｈ、厚さ１ｍｍの白金るつぼに、原料としてＺｎＯ、ＰｂＦ２、およびＰｂＯをそれぞれ、３２．２４ｇ、９２２．５８ｇおよび８３９．８８ｇ仕込んだ。このときの溶質であるＺｎＯの濃度は５ｍｏｌ％で、溶媒であるＰｂＦ２およびＰｂＯの濃度は、ＰｂＦ２：ＰｂＯ＝５０ｍｏｌ％：５０．０ｍｏｌ％となる。原料を仕込んだるつぼを図４に示す炉に設置し、るつぼ底温度を約９４０℃で１時間保持し、Ｐｔ攪拌冶具で攪拌し溶解させた。その後、るつぼ底温度が約８３５℃になるまで降温してから、水熱合成法で育成した＋ｃ面方位でサイズが１０ｍｍ×１０ｍｍ×５２９μｍｔのＺｎＯ単結晶基板を種結晶として接液し、引上軸を３０ｒｐｍで回転させながら同温度で８０時間成長させた。また、Ｈ１、Ｈ２、Ｈ３の設定温度は、オフセット差を維持したまま、－０．１℃／ｈｒの速度で降温させた。また、ＬＰＥ成長の間、すなわち８０時間かけて引上げ軸を連続的に５００μｍ程度引上げた。このときの軸引上げ速度は約６．３μｍ／ｈｒとなる。また、このとき軸回転方向は２分おきに反転させた。その後、引上軸を上昇させることで、融液から切り離し、１００ｒｐｍで軸を回転させることで、融液成分を振り切り、その後室温まで徐冷して無色透明のＺｎＯ単結晶を得た。室温まで冷却後、成長膜をＬＰＥ炉から取出しＰｔ治工具周辺を観察したがフラックス析出は見られなかった。ＬＰＥ成長厚は３４３μｍで、このときの成長速度は、約４．３μｍ／ｈｒであった。続いて、以下に示す自立化処理を施した。裏面（水熱合成基板の－ｃ面側）を、セラミックスプレートにＷＡＸで固定した。横型平面研削盤で＋ｃ面のＬＰＥ面が平坦になるよう約５０μｍ研削処理した。その後、表裏を張替え、水熱合成基板の厚みに相当する量を研削処理することで自立ＺｎＯ単結晶を得た。厚みは約２５１μｍ程度であった。自立膜をセラミックスプレートに再度ＷＡＸ固定し、ダイヤモンドスラリーでラップ処理を、コロイダルシリカでポリッシュ処理を施した。自立膜の表裏の研磨量は、＋ｃ面で２４μｍ、－ｃ面で１８μｍであり、結果厚さ約２５１μｍの自立ＺｎＯ単結晶を得た。研削、研磨の過程でクラックの発生はなかった。自立化処理後、±ｃ面をＳＩＭＳで分析し、Ｌｉ濃度を求めた。±ｃ面ともＬｉ濃度は検出下限である５×１０１３個／ｃｍ３以下であった。自立膜の結晶性を示す（００２）面のロッキングカーブ半値幅は約３１ａｒｃｓｅｃで結晶性が高いことを示している。伝導性を示すキャリヤ濃度は１．０×１０１９個／ｃｍ３、キャリヤ移動度は６０ｃｍ２／Ｖ・ｓｅｃとなった。キャリヤ移動度の高さからも品質が高いことを示している。自立膜中央部５０μｍ四方についてＡＦＭで平坦性を評価したところ、Ｒａ＝０．３ｎｍであった。
Figure JPOXMLDOC01-appb-T000006
 (Example 23)

A ZnO single crystal was produced by a liquid phase epitaxial method according to the following steps. Into a platinum crucible having an inner diameter of 75 mmΦ, a height of 75 mmh, and a thickness of 1 mm, 32.24 g, 922.58 g, and 839.88 g of ZnO, PbF 2 , and PbO were charged as raw materials, respectively. At this time, the concentration of ZnO as a solute is 5 mol%, and the concentrations of PbF 2 and PbO as solvents are PbF 2 : PbO = 50 mol%: 50.0 mol%. The crucible charged with the raw material was placed in the furnace shown in FIG. 4, the bottom temperature of the crucible was maintained at about 940 ° C. for 1 hour, and the mixture was stirred and dissolved with a Pt stirring jig. After that, the temperature is lowered until the bottom temperature of the crucible reaches about 835 ° C., and a ZnO single crystal substrate having a size of 10 mm × 10 mm × 529 μmt grown in a hydrothermal synthesis method and having a size of 10 mm × 10 mm × 529 μmt is contacted as a seed crystal. The shaft was grown at the same temperature for 80 hours while rotating the shaft at 30 rpm. The set temperatures of H1, H2, and H3 were decreased at a rate of −0.1 ° C./hr while maintaining the offset difference. Further, during the LPE growth, that is, over 80 hours, the pulling axis was continuously pulled up by about 500 μm. The shaft pulling speed at this time is about 6.3 μm / hr. At this time, the shaft rotation direction was reversed every two minutes. Thereafter, the pulling-up shaft was raised to separate it from the melt, and the shaft was rotated at 100 rpm to shake off the melt components and then gradually cooled to room temperature to obtain a colorless and transparent ZnO single crystal. After cooling to room temperature, the grown film was taken out from the LPE furnace and observed around the Pt jig, but no flux deposition was observed. The LPE growth thickness was 343 μm, and the growth rate at this time was about 4.3 μm / hr. Subsequently, the following independence treatment was performed. The back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX. About 50 μm was ground so that the + c plane LPE surface was flattened by a horizontal surface grinder. Then, the self-supporting ZnO single crystal was obtained by reversing the front and back and grinding the amount corresponding to the thickness of the hydrothermal synthetic substrate. The thickness was about 251 μm. The self-supporting film was fixed to the ceramic plate again by WAX, lapped with diamond slurry, and polished with colloidal silica. The polishing amount of the front and back surfaces of the free-standing film was 24 μm on the + c plane and 18 μm on the −c plane, and as a result, a free-standing ZnO single crystal having a thickness of about 251 μm was obtained. There were no cracks in the grinding and polishing process. After the self-supporting treatment, the ± c plane was analyzed by SIMS to determine the Li concentration. The Li concentration was 5 × 10 13 pieces / cm 3 or less, which is the lower limit of detection, on both the ± c planes. The rocking curve half-value width of the (002) plane showing the crystallinity of the free-standing film is about 31 arcsec, indicating that the crystallinity is high. The carrier concentration showing conductivity was 1.0 × 10 19 atoms / cm 3 , and the carrier mobility was 60 cm 2 / V · sec. It shows that the quality is high also from the high carrier mobility. When the flatness was evaluated by AFM for the 50 μm square portion of the self-supporting film, Ra = 0.3 nm.

　本実施例では、成長したＺｎＯに導電性を付与するドーパントを加えていないが、溶媒に用いたＰｂＦ２からのＦドープが導電性発現要因になったと思われる。以上の結果から、ＰｂＦ２およびＰｂＯ溶媒を用いても、自立導電性ＺｎＯ単結晶を、Ｌｉ濃度１×１０１５個／ｃｍ３以下で製造することが可能となることを示している。一方、同溶媒ではＦが導電性発現元素となっており、ドーパント仕込み量で伝導性を制御することは困難となる。
In this example, a dopant imparting conductivity was not added to the grown ZnO, but it seems that F doping from PbF 2 used as a solvent became a cause of conductivity. From the above results, it is shown that a self-standing conductive ZnO single crystal can be produced at a Li concentration of 1 × 10 15 pieces / cm 3 or less even when PbF 2 and PbO solvents are used. On the other hand, in the same solvent, F is a conductive expression element, and it is difficult to control the conductivity with the amount of dopant charged.
Figure JPOXMLDOC01-appb-T000007
 （実施例２４－２５）
Figure JPOXMLDOC01-appb-T000007
 (Examples 24-25)
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
 　実施例９において、連続的な軸引上げ速度を２．０μｍ／ｈｒとした以外、実施例９と同様に実施例２４を行った。実施例９において、連続的な軸引上げ速度を５０．０μｍ／ｈｒとした以外、実施例９と同様に実施例２５を行った。実施例２４－２５ではクラック発生なしに自立膜を製造することができた。実施例２４および２５で得た自立化膜の物性面では、格子定数やバンドギャップは実施例９とほとんど同じであったが、成長速度が低い実施例２４では、（００２）面のロッキングカーブ半値幅が狭まり、結晶性の良化が見られた。一方、成長速度が速い実施例２５では（００２）面のロッキングカーブ半値幅が拡がり、結晶性の低下が見られた。
Figure JPOXMLDOC01-appb-T000009
 In Example 9, Example 24 was performed in the same manner as in Example 9 except that the continuous shaft pulling rate was 2.0 μm / hr. In Example 9, Example 25 was performed in the same manner as Example 9 except that the continuous shaft pulling rate was 50.0 μm / hr. In Examples 24-25, a self-supporting film could be produced without generation of cracks. In the physical properties of the self-supporting films obtained in Examples 24 and 25, the lattice constant and the band gap were almost the same as those in Example 9, but in Example 24 where the growth rate was low, the rocking curve half of the (002) plane was used. The value range narrowed and the crystallinity improved. On the other hand, in Example 25 where the growth rate was high, the full width at half maximum of the rocking curve on the (002) plane was widened, and a decrease in crystallinity was observed.

　以下、本発明の一実施形態に係わるＭｇ含有ＺｎＯ系混晶単結晶の育成法として、ＺｎＯ基板単結晶上にＭｇ含有ＺｎＯ系混晶単結晶を液相エピタキシャル成長法によって成長させる方法について説明する。本発明は、以下の実施例に何ら限定されるものではない。
Hereinafter, as a method for growing an Mg-containing ZnO mixed crystal single crystal according to an embodiment of the present invention, a method of growing an Mg-containing ZnO mixed crystal single crystal on a ZnO substrate single crystal by a liquid phase epitaxial growth method will be described. The present invention is not limited to the following examples.
（実施例２６）
　以下の工程により、Ｍｇ含有ＺｎＯ系混晶単結晶を液相エピタキシャル（Liquid phase epitaxial：ＬＰＥ）成長法で作製した。内径７５ｍｍΦ、高さ７５ｍｍｈ、厚さ１ｍｍの白金るつぼに、原料としてＺｎＯ、ＭｇＯ、Ａｌ２Ｏ３、ＰｂＯ、およびＢｉ２Ｏ３をそれぞれ、３２．９４ｇ、１．８１ｇ、０．００２ｇ、８００．６１ｇおよび８３４．３９ｇ仕込んだ。このときの溶質であるＺｎＯの濃度は７ｍｏｌ％で、ＺｎとＭｇの比はＭｇＯ／（ＺｎＯ＋ＭｇＯ）＝１０ｍｏｌ％で、溶媒であるＰｂＯおよびＢｉ２Ｏ３の濃度は、ＰｂＯ：Ｂｉ２Ｏ３＝６６．７ｍｏｌ％：３３．３ｍｏｌ％となる。原料を仕込んだるつぼを図４に示す炉に設置し、るつぼ底温度約８４０℃で１時間保持しＰｔ攪拌冶具で攪拌し溶解させた。その後、るつぼ底温度が約８０８℃になるまで降温してから、水熱合成法で育成した＋ｃ面方位でサイズが１０ｍｍ×１０ｍｍ×５３８μｍｔのＺｎＯ単結晶基板を種結晶として接液し、引上軸を３０ｒｐｍで回転させながら同温度で８０時間成長させた。また、Ｈ１、Ｈ２、Ｈ３の設定温度は、オフセット差を維持したまま、－０．１℃／ｈｒの速度で降温させた。また、ＬＰＥ成長の間、すなわち８０時間かけて連続的に引上げ軸を５００μｍ程度引上げた。このときの軸引上げ速度は約６．３μｍ／ｈｒとなる。このとき、軸回転方向は２分おきに反転させた。その後、引上軸を上昇させることで、融液から切り離し、１００ｒｐｍで軸を回転させることで、融液成分を振り切り、その後室温まで徐冷して無色透明のＭｇ含有ＺｎＯ系混晶単結晶をクラックフリーで得た。ＬＰＥ成長膜厚は３９７μｍで、このときの成長速度は、約５．０μｍ／ｈｒであった。続いて、以下に示す自立化処理を施した。裏面（水熱合成基板の－ｃ面側）を、セラミックスプレートにＷＡＸで固定した。横型平面研削盤で＋ｃ面のＬＰＥ面が平坦になるよう約５０μｍ研削処理した。その後、表裏を張替え、水熱合成基板の厚みに相当する量を研削処理することで自立Ｍｇ含有ＺｎＯ系混晶単結晶を得た。厚みは約３４７μｍ程度であった。自立膜をセラミックスプレートに再度ＷＡＸ固定し、ダイヤモンドスラリーでラップ処理を、コロイダルシリカでポリッシュ処理を施した。自立膜の表裏の研磨量は、＋面で３３μｍ、－面で２８μｍであった。自立膜中央部５０μｍ四方について原子間力顕微鏡（Atomic Force Microscopy：ＡＦＭ）で平坦性を評価したところ、Ｒａ＝０．３ｎｍであった。 (Example 26)
An Mg-containing ZnO-based mixed crystal single crystal was produced by a liquid phase epitaxial (LPE) growth method through the following steps. In a platinum crucible having an inner diameter of 75 mmΦ, a height of 75 mmh, and a thickness of 1 mm, ZnO, MgO, Al 2 O 3 , PbO, and Bi 2 O 3 as raw materials were respectively 32.94 g, 1.81 g, 0.002 g, 800. 61 g and 834.39 g were charged. The concentration of ZnO as a solute at this time is 7 mol%, the ratio of Zn to Mg is MgO / (ZnO + MgO) = 10 mol%, and the concentrations of PbO and Bi 2 O 3 as solvents are PbO: Bi 2 O 3 = 66.7 mol%: 33.3 mol%. The crucible charged with the raw material was placed in the furnace shown in FIG. 4, held at a crucible bottom temperature of about 840 ° C. for 1 hour, and stirred and melted with a Pt stirring jig. Thereafter, the temperature is lowered until the bottom temperature of the crucible reaches about 808 ° C., and a ZnO single crystal substrate having a size of 10 mm × 10 mm × 538 μmt grown in a hydrothermal synthesis method and having a size of 10 mm × 10 mm × 538 μmt is brought into contact with the seed crystal as a seed crystal. The shaft was grown at the same temperature for 80 hours while rotating the shaft at 30 rpm. The set temperatures of H1, H2, and H3 were decreased at a rate of −0.1 ° C./hr while maintaining the offset difference. Further, during the LPE growth, that is, over 80 hours, the pulling axis was continuously pulled up by about 500 μm. The shaft pulling speed at this time is about 6.3 μm / hr. At this time, the shaft rotation direction was reversed every two minutes. Thereafter, the pulling-up shaft is raised to separate it from the melt, and the shaft is rotated at 100 rpm to shake off the melt components, and then slowly cooled to room temperature to form a colorless and transparent Mg-containing ZnO-based mixed crystal single crystal. Obtained crack-free. The LPE growth film thickness was 397 μm, and the growth rate at this time was about 5.0 μm / hr. Subsequently, the following independence treatment was performed. The back surface (the -c surface side of the hydrothermal synthesis substrate) was fixed to the ceramic plate with WAX. About 50 μm was ground so that the + c plane LPE surface was flattened by a horizontal surface grinder. Thereafter, the front and back surfaces were changed over, and an amount corresponding to the thickness of the hydrothermal synthesis substrate was ground to obtain a self-supporting Mg-containing ZnO mixed single crystal. The thickness was about 347 μm. The self-supporting film was fixed to the ceramic plate again by WAX, lapped with diamond slurry, and polished with colloidal silica. The polishing amount of the front and back surfaces of the self-supporting film was 33 μm on the + surface and 28 μm on the − surface. When flatness was evaluated with an atomic force microscope (AFM) for the 50 μm square of the center of the free-standing film, Ra = 0.3 nm.

　次に、得られた自立膜の表裏面についてＰＬ発光波長の分布測定を行ったところ、表裏面とも３５７．５ｎｍ±０．２ｎｍの分布となった。これをバンドギャップに換算すると、Ｅｇ＝３．４６８ｅＶ±０．００２ｅＶとなる。Ｍｇ含有ＺｎＯ系混晶単結晶では、Ｍｇ／（Ｚｎ＋Ｍｇ）組成が１０％±１％（組成変化では±１０％に相当）変動するとＰＬ発光波長が３５７．５ｎｍ±２．１ｎｍ程度、バンドギャップが３．４６８ｅＶ±０．２０ｅＶ程度変化するので、実施例２６における自立化膜のＭｇ／（Ｚｎ＋Ｍｇ）均一性は約±１％となり、同様にバンドギャップ均一性は約±０．６％となる。また、得られた自立化膜をｃ面に垂直に切断した面のＣＬ発光波長分布を測定したところ、ＰＬ発光波長と同じＥｇ＝３．４６８ｅＶ±０．２ｎｍとなった。以上の結果から、実施例２６における自立化膜のＭｇ／（Ｚｎ＋Ｍｇ）均一性は±１％以内となり、面内方向および膜厚方向何れの方向においても組成均一性は±１０％以内であることを示している。
　続いて、自立化膜表裏面とｃ面に垂直に切断した面についてダイナミックＳＩＭＳを用いてＬｉ濃度を測定したところ、何れの面においてもＬｉ濃度は、検出下限である５×１０１３個／ｃｍ３以下であった。
　実施例２６におけるＬＰＥ成長条件、研削および研磨膜厚、物性を表１０に示す。尚、「キャリヤ濃度」および「キャリヤ移動度」は、東陽テクニカ製ホール効果・比抵抗測定装置を用い、Ｖａｎ Ｄｅｒ　Ｐａｕｗ法により室温で測定した。
Next, when the distribution of the PL emission wavelength was measured on the front and back surfaces of the obtained self-supporting film, the distribution was 357.5 nm ± 0.2 nm on both the front and back surfaces. When this is converted into a band gap, Eg = 3.468 eV ± 0.002 eV. In the Mg-containing ZnO mixed crystal single crystal, when the Mg / (Zn + Mg) composition varies by 10% ± 1% (corresponding to ± 10% in composition change), the PL emission wavelength is about 357.5 nm ± 2.1 nm, and the band gap is Since it changes by about 3.468 eV ± 0.20 eV, the Mg / (Zn + Mg) uniformity of the self-supporting film in Example 26 is about ± 1%, and similarly the band gap uniformity is about ± 0.6%. Further, when the CL emission wavelength distribution of the surface obtained by cutting the obtained self-supporting film perpendicularly to the c-plane was measured, Eg = 3.468 eV ± 0.2 nm which was the same as the PL emission wavelength. From the above results, the Mg / (Zn + Mg) uniformity of the self-supporting film in Example 26 is within ± 1%, and the composition uniformity is within ± 10% in both the in-plane direction and the film thickness direction. Is shown.
Subsequently, when Li concentration was measured using dynamic SIMS on the front and back surfaces of the self-supporting film and the surface cut perpendicular to the c-plane, the Li concentration was 5 × 10 13 pieces / cm which is the lower limit of detection on any surface. 3 or less.
Table 10 shows LPE growth conditions, grinding and polishing film thickness, and physical properties in Example 26. The “carrier concentration” and “carrier mobility” were measured at room temperature by the Van Der Pauw method using a Hall effect / specific resistance measuring device manufactured by Toyo Technica.
Figure JPOXMLDOC01-appb-T000010
 実施例２７－３１
　実施例２６のＭｇＯ仕込み組成と軸引上げ方式を変えて表１１の方法で自立化膜を得た。何れの膜においてもＰＬ発光波長から求めたバンドギャップは３．３２から３．５４ｅＶで、水熱合成基板よりバンドギャップがワイド化された自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーとなっていることを示している。また、何れの膜においても（００２）面ロッキングカーブ半値幅は２７－４５ａｒｃｓｅｃで高い結晶性を有している。また、自立化処理後の表裏面のＬｉ濃度は全て検出下限以下の５×１０１３個／ｃｍ３以下であった。
　一方、実施例３１では、軸引上げ方法を連続的から間欠的に変更した。軸を停止させて１６時間経過したら軸を１００μｍ引上げる工程を５回繰り返し、８０時間で軸を合計５００μｍ引上げた。引上げ平均速度は６．３μｍ／ｈｒで実施例３０の引上げ速度と同じである。結晶性を示す（００２）面のロッキングカーブ半値幅では、実施例３１の方が結晶性が低下している。間欠的引上げを行うと、軸を引上げたときの結晶成長の不安定性を反映した結果と思われる。
Figure JPOXMLDOC01-appb-T000010
 Examples 27-31
A self-supporting film was obtained by the method shown in Table 11 while changing the MgO preparation composition and the shaft pulling method of Example 26. In any film, the band gap obtained from the PL emission wavelength is 3.32 to 3.54 eV, and the film is a self-supporting Mg-containing ZnO mixed single crystal wafer having a wider band gap than the hydrothermal synthetic substrate. Is shown. In any film, the (002) plane rocking curve half-width is 27-45 arcsec and has high crystallinity. In addition, the Li concentrations on the front and back surfaces after the self-supporting treatment were all 5 × 10 13 pieces / cm 3 or less, which were below the detection lower limit.
On the other hand, in Example 31, the shaft pulling method was changed from continuous to intermittent. When the shaft was stopped and 16 hours passed, the step of lifting the shaft by 100 μm was repeated 5 times, and the shaft was pulled by a total of 500 μm in 80 hours. The pulling average speed is 6.3 μm / hr, which is the same as the pulling speed of Example 30. In the rocking curve half width of the (002) plane showing crystallinity, the crystallinity of Example 31 is lower. The intermittent pulling seems to reflect the instability of crystal growth when the shaft is pulled up.
Figure JPOXMLDOC01-appb-T000011
 比較例３－７
　軸引上げを行わなかったこと以外は、実施例２７－３１と同じ方法で自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー膜を製造した。何れの成長膜においてもＰｔ治工具を基点としたフラックス析出が見られ、成長中、冷却中、研削／研磨の何れかの工程でクラックが発生した。以上の結果より、自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーを得るための厚膜成長を行う場合、軸引上げ成長を行うことで、Ｐｔ治工具を基点としたフラックス析出を抑制することが可能となることがわかる。フラックス析出が抑制されると、成長、冷却および研削／研磨の各工程でのクラック発生を低減することが可能となる。
Figure JPOXMLDOC01-appb-T000011
 Comparative Example 3-7
A self-supporting Mg-containing ZnO mixed single crystal wafer film was produced in the same manner as in Examples 27-31 except that the shaft was not pulled up. In any growth film, flux precipitation based on the Pt jig was observed, and cracks occurred during any of the growth, cooling, and grinding / polishing steps. From the above results, when performing thick film growth to obtain a self-supporting Mg-containing ZnO mixed crystal single crystal wafer, it is possible to suppress flux precipitation based on the Pt jig by performing axial pulling growth. I understand that When the flux precipitation is suppressed, it is possible to reduce the generation of cracks in the growth, cooling and grinding / polishing steps.

実施例３２－３３
Examples 32-33
Figure JPOXMLDOC01-appb-T000012
 　実施例３１において、間欠的な軸引上げを連続的な軸引上げに変更し、連続的な軸引上げ速度を２．０μｍ／ｈｒに変更した以外は、実施例３１と同様に実施例３２を行った。実施例３１において、間欠的な軸引上げを連続的な軸引上げに変更し、連続的な軸引上げ速度を５０．０μｍ／ｈｒとし、成長時間を８０時間から４０時間に変更した以外、実施例３１と同様に実施例３３を行った。実施例３２及び３３では、クラック発生なしに自立膜を製造することができた。実施例３２および３３で得た自立化膜の物性面では、格子定数やバンドギャップは実施例３１とほとんど同じであったが、成長速度が低い実施例３２では、（００２）面のロッキングカーブ半値幅が狭まり、結晶性の良化が見られた。一方、成長速度が速い実施例３３では（００２）面のロッキングカーブ半値幅が拡がり、結晶性の低下が見られた。
Figure JPOXMLDOC01-appb-T000012
 In Example 31, Example 32 was performed in the same manner as in Example 31 except that the intermittent shaft pulling was changed to continuous shaft pulling and the continuous shaft pulling speed was changed to 2.0 μm / hr. . In Example 31, except that the intermittent axial pulling was changed to continuous axial pulling, the continuous axial pulling speed was changed to 50.0 μm / hr, and the growth time was changed from 80 hours to 40 hours. Example 33 was carried out in the same manner as above. In Examples 32 and 33, a self-supporting film could be produced without generation of cracks. In the physical properties of the self-supporting films obtained in Examples 32 and 33, the lattice constant and the band gap were almost the same as in Example 31, but in Example 32 where the growth rate was low, the (002) plane rocking curve half The value range narrowed and the crystallinity improved. On the other hand, in Example 33 having a high growth rate, the rocking curve half-value width of the (002) plane was widened, and the crystallinity was lowered.
　本発明は、ＺｎＯ系半導体材料に関し、特に、光学分野、電気・電子工業分野において利用可能である。
　 The present invention relates to a ZnO-based semiconductor material, and can be used particularly in the fields of optics and electric / electronic industries.

Claims (35)

  1. 　溶質であるＺｎＯと溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＺｎＯ単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法。 After the solute ZnO and the solvent are mixed and melted, the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is pulled up continuously or intermittently to form a ZnO single crystal. And a step of growing a crystal on the seed crystal substrate. A method for producing a ZnO single crystal by a liquid phase epitaxial growth method.
  2. 　前記溶媒がＰｂＯおよびＢｉ２Ｏ３である請求項１に記載の液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法。 The method for producing a ZnO single crystal by a liquid phase epitaxial growth method according to claim 1, wherein the solvent is PbO and Bi 2 O 3 .
  3. 　前記溶質と溶媒の混合比が、溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％であり、溶媒であるＰｂＯとＢｉ２Ｏ３の混合比がＰｂＯ：Ｂｉ２Ｏ３＝０．１～９５ｍｏｌ％：９９．９～５ｍｏｌ％である請求項２に記載のＺｎＯ単結晶の製造方法。 The mixing ratio of the solute and the solvent is solute: solvent = 5 to 30 mol%: 95 to 70 mol%, and the mixing ratio of the solvent PbO and Bi 2 O 3 is PbO: Bi 2 O 3 = 0.1 to 95 mol. The method for producing a ZnO single crystal according to claim 2, wherein%: 99.9 to 5 mol%.
  4. 　前記溶媒がＰｂＦ２およびＰｂＯである請求項１に記載の液相エピタキシャル成長法によるＺｎＯ単結晶の製造方法。 The method for producing a ZnO single crystal by a liquid phase epitaxial growth method according to claim 1, wherein the solvent is PbF 2 or PbO.
  5. 　前記溶質と溶媒の混合比が、溶質：溶媒＝２～２０ｍｏｌ％：９８～８０ｍｏｌ％であり、溶媒であるＰｂＦ２とＰｂＯの混合比がＰｂＦ２：ＰｂＯ＝２０～８０ｍｏｌ％：８０～２０ｍｏｌ％である請求項４に記載のＺｎＯ単結晶の製造方法。 The mixing ratio of the solute and the solvent is solute: solvent = 2 to 20 mol%: 98 to 80 mol%, and the mixing ratio of PbF 2 and PbO as the solvent is PbF 2 : PbO = 20 to 80 mol%: 80 to 20 mol%. The method for producing a ZnO single crystal according to claim 4.

  6. 　連続的に種結晶基板を引上げる速度Ｖが、２μｍ／ｈｒ≦Ｖ≦５０μｍ／ｈｒである請求項１から５のいずれかに記載のＺｎＯ系単結晶の製造方法。
    The method for producing a ZnO-based single crystal according to any one of claims 1 to 5, wherein a speed V for continuously pulling up the seed crystal substrate is 2 µm / hr ≤ V ≤ 50 µm / hr.

  7. 　間欠的に種結晶基板を引上げる平均速度ｖが、２μｍ／ｈｒ≦ｖ≦５０μｍ／ｈｒである請求項１から５のいずれかに記載のＺｎＯ系単結晶の製造方法。
    6. The method for producing a ZnO-based single crystal according to claim 1, wherein an average speed v for intermittently pulling the seed crystal substrate is 2 μm / hr ≦ v ≦ 50 μm / hr.
  8. 　前記ＺｎＯ単結晶の膜厚が１００μｍ以上である請求項１から７のいずれかに記載のＺｎＯ系単結晶の製造方法。 The method for producing a ZnO-based single crystal according to any one of claims 1 to 7, wherein a film thickness of the ZnO single crystal is 100 µm or more.
  9. 　前記ＺｎＯ単結晶が、Ａｌ、Ｇａ、Ｉｎ、Ｈ、およびＦからなる群より選択される１以上を含有する請求項１から８のいずれかに記載のＺｎＯ単結晶の製造方法。 The method for producing a ZnO single crystal according to any one of claims 1 to 8, wherein the ZnO single crystal contains one or more selected from the group consisting of Al, Ga, In, H, and F.
  10. 　前記ＺｎＯ単結晶の成長方位が＋ｃ面である請求項１から９のいずれかに記載のＺｎＯ系単結晶の製造方法。 The method for producing a ZnO-based single crystal according to any one of claims 1 to 9, wherein the growth orientation of the ZnO single crystal is a + c plane.
  11. 　前記ＺｎＯ単結晶を成長させた後、前記種結晶基板を研磨またはエッチングで除去し、前記単結晶の液相エピタキシャル成長した－ｃ面側を少なくとも１０μｍ以上研磨あるいはエッチングする工程を有する、請求項１から１０のいずれかに記載のＺｎＯ単結晶の製造方法。 2. The method according to claim 1, further comprising a step of growing the ZnO single crystal, removing the seed crystal substrate by polishing or etching, and polishing or etching at least 10 μm or more on the −c plane side of the liquid crystal epitaxial growth of the single crystal. 10. A method for producing a ZnO single crystal according to any one of 10 above.
  12. 　請求項１１に記載のＺｎＯ単結晶の製造方法によって得られた自立ＺｎＯ単結晶ウエファーであって、膜厚が１００μｍ以上であることを特徴とする自立ＺｎＯ単結晶ウエファー。
    A self-standing ZnO single crystal wafer obtained by the method for producing a ZnO single crystal according to claim 11, wherein the film thickness is 100 μm or more.
  13. Ｌｉ濃度が、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、１×１０１５個／ｃｍ３以下である請求項１２に記載の自立ＺｎＯ単結晶ウエファー。
    The self-standing ZnO single crystal wafer according to claim 12, wherein the Li concentration is uniform in the in-plane direction and the thickness direction of the wafer, and is 1 x 10 15 pieces / cm 3 or less.
  14. Ｇａを含有し、キャリヤ濃度が２．０×１０１７個／ｃｍ３～１．０×１０１９個／ｃｍ３であり、かつ、Ｌｉ濃度が１ｅ１５個／ｃｍ３以下である請求項１２または１３に記載の自立ＺｎＯ単結晶ウエファー。
    The Ga-containing material has a carrier concentration of 2.0 × 10 17 pcs / cm 3 to 1.0 × 10 19 pcs / cm 3 and a Li concentration of 1e 15 pcs / cm 3 or less. The self-supporting ZnO single crystal wafer according to 13.
  15. Ａｌを含有し、キャリヤ濃度が２．０×１０１７個／ｃｍ３～１．０×１０１９個／ｃｍ３であり、かつ、Ｌｉ濃度が１×１０１５個／ｃｍ３以下である請求項１２または１３に記載の自立ＺｎＯ単結晶ウエファー。
    Al is contained, the carrier concentration is 2.0 × 10 17 pieces / cm 3 to 1.0 × 10 19 pieces / cm 3 , and the Li concentration is 1 × 10 15 pieces / cm 3 or less. The self-standing ZnO single crystal wafer according to 12 or 13.
  16. Ｉｎを含有し、キャリヤ濃度が２．０ｅ１７個／ｃｍ３～３．５×１０１７個／ｃｍ３であり、かつ、Ｌｉ濃度が１×１０１５個／ｃｍ３以下である請求項１２または１３に記載の自立ＺｎＯ単結晶ウエファー。 13. In, wherein the carrier concentration is 2.0e 17 pieces / cm 3 to 3.5 × 10 17 pieces / cm 3 , and the Li concentration is 1 × 10 15 pieces / cm 3 or less. The self-supporting ZnO single crystal wafer according to 13.

  17. 　厚み５０μｍ以上の板状形状を有し、板の厚み方向、および、面内方向の何れに対しても均一なＺｎとＭｇとの化学組成を有し、かつ、表裏面のうち少なくとも１面がエピタキシャル成長可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。
    It has a plate-like shape with a thickness of 50 μm or more, has a uniform chemical composition of Zn and Mg in both the thickness direction of the plate and the in-plane direction, and at least one of the front and back surfaces is A self-standing Mg-containing ZnO mixed single crystal wafer characterized by having flatness capable of epitaxial growth.
  18. 　バンドギャップ（Ｅｇ）値が、ウエファーの面内方向、および、厚み方向に対して均一であり、かつ、３．３０ｅＶを超える請求項１７に記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 The self-standing Mg-containing ZnO mixed single crystal wafer according to claim 17, wherein the band gap (Eg) value is uniform in the in-plane direction and thickness direction of the wafer and exceeds 3.30 eV.
  19. 　Ｌｉ濃度が、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、１×１０１５個／ｃｍ３以下である請求項１７または１８に記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 The self-standing Mg-containing ZnO-based mixed crystal single crystal according to claim 17 or 18, wherein the Li concentration is uniform in the in-plane direction and the thickness direction of the wafer, and is 1 x 10 15 pieces / cm 3 or less. Wafer.
  20. 　Ａｌ、Ｇａ、Ｉｎ、Ｈ、およびＦからなる群より選択される１以上を含有する請求項１７から１９のいずれかに記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 The self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer according to any one of claims 17 to 19, containing at least one selected from the group consisting of Al, Ga, In, H, and F.
  21. 　溶質であるＺｎＯおよびＭｇＯと溶媒とを混合して融解させた後、得られた融液に、種結晶基板を直接接触させる工程と、前記種結晶基板を連続的あるいは間欠的に引上げることによってＭｇ含有ＺｎＯ系混晶単結晶を前記種結晶基板上に成長させる工程と、を有することを特徴とする液相エピタキシャル成長法によるＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 After mixing and melting solute ZnO and MgO and a solvent, the seed crystal substrate is brought into direct contact with the obtained melt, and the seed crystal substrate is pulled up continuously or intermittently. And a step of growing an Mg-containing ZnO mixed crystal single crystal on the seed crystal substrate. A method for producing an Mg-containing ZnO mixed crystal single crystal by a liquid phase epitaxial growth method.
  22. 　前記溶媒がＰｂＯおよびＢｉ２Ｏ３である請求項２１に記載の液相エピタキシャル成長法によるＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 The method for producing a Mg-containing ZnO mixed crystal single crystal by a liquid phase epitaxial growth method according to claim 21, wherein the solvent is PbO and Bi 2 O 3 .
  23. 前記溶質と溶媒との混合比が、ＺｎＯのみに換算した溶質：溶媒＝５～３０ｍｏｌ％：９５～７０ｍｏｌ％であり、溶媒であるＰｂＯとＢｉ２Ｏ３との混合比が、ＰｂＯ：Ｂｉ２Ｏ３＝０．１～９５ｍｏｌ％：９９．９～５ｍｏｌ％である請求項２２に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 The mixing ratio of the solute and the solvent is solute converted to ZnO only: solvent = 5 to 30 mol%: 95 to 70 mol%, and the mixing ratio of PbO and Bi 2 O 3 as the solvent is PbO: Bi 2. The method for producing an Mg-containing ZnO mixed crystal single crystal according to claim 22, wherein O 3 = 0.1 to 95 mol%: 99.9 to 5 mol%.
  24. 　前記溶媒がＰｂＦ２およびＰｂＯである請求項２１に記載の液相エピタキシャル成長法によるＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 The method for producing an Mg-containing ZnO mixed crystal single crystal by a liquid phase epitaxial growth method according to claim 21, wherein the solvent is PbF 2 and PbO.
  25. 　前記溶質と溶媒との混合比が、ＺｎＯのみに換算した溶質：溶媒＝２～２０ｍｏｌ％：９８～８０ｍｏｌ％であり、溶媒であるＰｂＦ２とＰｂＯとの混合比が、ＰｂＦ２：ＰｂＯ＝８０～２０ｍｏｌ％：２０～８０ｍｏｌ％である請求項２４に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。
    The mixing ratio of the solute and the solvent is solute converted to ZnO only: solvent = 2 to 20 mol%: 98 to 80 mol%, and the mixing ratio of PbF 2 and PbO as the solvent is PbF 2 : PbO = 80. The method for producing a Mg-containing ZnO mixed crystal single crystal according to claim 24, wherein the content is -20 mol%: 20 to 80 mol%.
  26. 　連続的に種結晶基板を引上げる速度Ｖが、２μｍ／ｈｒ≦Ｖ≦５０μｍ／ｈｒである請求項２１から２５のいずれかに記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 26. The method for producing an Mg-containing ZnO mixed single crystal according to any one of claims 21 to 25, wherein the rate V of continuously pulling up the seed crystal substrate is 2 μm / hr ≦ V ≦ 50 μm / hr.
  27. 　間欠的に種結晶基板を引上げる平均速度ｖが、２μｍ／ｈｒ≦ｖ≦５０μｍ／ｈｒである請求項２１から２５のいずれかに記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 The method for producing an Mg-containing ZnO mixed single crystal according to any one of claims 21 to 25, wherein an average speed v of intermittently pulling the seed crystal substrate is 2 µm / hr ≤ v ≤ 50 µm / hr.
  28. 　前記Ｍｇ含有ＺｎＯ系混晶単結晶の膜厚が１００μｍ以上である請求項２１から２７のいずれかに記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。
    The method for producing an Mg-containing ZnO mixed crystal single crystal according to any one of claims 21 to 27, wherein a film thickness of the Mg-containing ZnO mixed crystal single crystal is 100 µm or more.
  29. 　前記Ｍｇ含有ＺｎＯ系混晶単結晶の成長方位が＋ｃ面である請求項２１から２８のいずれかに記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 The method for producing an Mg-containing ZnO mixed crystal single crystal according to any one of claims 21 to 28, wherein a growth orientation of the Mg-containing ZnO mixed crystal single crystal is a + c plane.
  30. 　前記Ｍｇ含有ＺｎＯ系混晶単結晶を成長させた後、前記種結晶基板を研磨またはエッチングで除去し、前記単結晶の液相エピタキシャル成長した－ｃ面側を少なくとも１０μｍ以上研磨またはエッチングする工程を有する、請求項２１から２９のいずれかに記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法。 After growing the Mg-containing ZnO mixed crystal single crystal, the step of removing the seed crystal substrate by polishing or etching, and polishing or etching at least 10 μm or more on the −c plane side of the single crystal subjected to liquid phase epitaxial growth. The manufacturing method of the Mg containing ZnO type mixed crystal single crystal in any one of Claim 21 to 29.
  31. 　請求項３０に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって自立Ｍｇ含有ＺｎＯ系混晶単結晶を製造した後、これを種結晶基板として用い、この基板上に更にＺｎＯあるいはＭｇ含有ＺｎＯ系混晶単結晶を成長させることを特徴とするＭｇ含有ＺｎＯ系混晶単結晶積層体の製造方法。 A self-supporting Mg-containing ZnO mixed single crystal is manufactured by the method for manufacturing an Mg-containing ZnO mixed single crystal according to claim 30, and then used as a seed crystal substrate. Further, ZnO or Mg-containing ZnO is further formed on the substrate. A method for producing a Mg-containing ZnO mixed crystal single crystal laminate, characterized by growing a mixed crystal single crystal.
  32. 　請求項３０に記載のＭｇ含有ＺｎＯ系混晶単結晶の製造方法によって得られた自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファーであって、５０μｍ以上の板状形状を有し、板の厚み方向、および、面内方向の何れに対しても均一なＺｎとＭｇとの化学組成を有し、かつ、表裏面のうち少なくとも１面がエピタキシャル成長可能な平坦性を有することを特徴とする自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 A self-supporting Mg-containing ZnO-based mixed crystal single crystal wafer obtained by the method for producing an Mg-containing ZnO-based mixed crystal single crystal according to claim 30, having a plate-like shape of 50 μm or more, the thickness direction of the plate, And a self-standing Mg-containing ZnO having a uniform chemical composition of Zn and Mg in any of the in-plane directions, and having flatness capable of epitaxial growth of at least one of the front and back surfaces Mixed crystal single crystal wafer.
  33. 　バンドギャップ（Ｅｇ）値が、ウエファーの面内方向、および、厚み方向に対して均一であり、かつ、３．３０ｅＶを超える請求項３２に記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 The self-standing Mg-containing ZnO-based mixed crystal single crystal wafer according to claim 32, wherein the band gap (Eg) value is uniform in the in-plane direction and the thickness direction of the wafer and exceeds 3.30 eV.
  34. 　Ｌｉ濃度が、ウエファーの面内方向、および、厚み方向に対し均一であり、かつ、１×１０１５個／ｃｍ３以下である請求項３２または３３に記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。 34. The self-supporting Mg-containing ZnO mixed single crystal according to claim 32 or 33, wherein the Li concentration is uniform in the in-plane direction and the thickness direction of the wafer and is 1 × 10 15 pieces / cm 3 or less. Wafer.
  35. 　Ａｌ、Ｇａ、Ｉｎ、Ｈ、およびＦからなる群より選択される１以上を含有する請求項３２から３４のいずれかに記載の自立Ｍｇ含有ＺｎＯ系混晶単結晶ウエファー。  35. The self-supporting Mg-containing ZnO mixed single crystal wafer according to any one of claims 32 to 34, which contains one or more selected from the group consisting of Al, Ga, In, H, and F.
PCT/JP2009/055301 2008-03-26 2009-03-18 Process for producing zno single crystal, self-supporting zno single-crystal wafer obtained by the same, self-supporting wafer of mg-containing zno mixed single crystal, and process for producing mg-containing zno mixed single crystal for use in the same WO2009119411A1 (en)

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US12/934,835 US20110024742A1 (en) 2008-03-26 2009-03-18 PROCESS FOR PRODUCING ZnO SINGLE CRYSTAL, SELF-SUPPORTING ZnO SINGLE-CRYSTAL WAFER OBTAINED BY THE SAME, SELF-SUPPORTING WAFER OF Mg-CONTAINING ZnO MIXED SINGLE CRYSTAL, AND PROCESS FOR PRODUCING Mg-CONTAINING ZnO MIXED SINGLE CRYSTAL FOR USE IN THE SAME
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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63144191A (en) * 1986-12-02 1988-06-16 Sumitomo Electric Ind Ltd Production of compound semiconductor single crystal and apparatus therefor
JP2000302596A (en) * 1999-04-15 2000-10-31 Fujikura Ltd Oxide superconductor and its production
JP2002009353A (en) * 2000-06-16 2002-01-11 Internatl Superconductivity Technology Center Bicrystal oxide superconducting film and high temperature superconducting josephson junction element and superconducting quantum inteference element using it
JP2003046081A (en) 2001-07-30 2003-02-14 Sharp Corp Semiconductor device
JP2005072067A (en) 2003-08-27 2005-03-17 National Institute For Materials Science Zinc oxide base multilayer structure and its fabricating process
JP2007100146A (en) 2005-09-30 2007-04-19 Dowa Holdings Co Ltd Cu-Ni-Sn-P-BASED COPPER ALLOY HAVING LESSENED ANISOTROPY OF STRESS RELAXATION RESISTANCE, AND MANUFACTURING METHOD THEREFOR
JP2007204324A (en) 2006-02-02 2007-08-16 Tokyo Denpa Co Ltd Manufacturing method of high purity zinc oxide single crystal, and high purity zinc oxide single crystal
JP2007223878A (en) * 2006-02-27 2007-09-06 Sumitomo Electric Ind Ltd Method for producing group iii nitride crystal and group iii nitride crystal substrate
WO2007100146A1 (en) * 2006-03-01 2007-09-07 Mitsubishi Gas Chemical Company, Inc. PROCESS FOR PRODUCING ZnO SINGLE CRYSTAL ACCORDING TO METHOD OF LIQUID PHASE GROWTH

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1063511A (en) * 1991-01-24 1992-08-12 中国科学院上海光学精密机械研究所 The growing apparatus of barium titanate tetragonal crystal and growth method
US6743533B1 (en) * 1999-04-15 2004-06-01 Fujikura Ltd. Oxide superconductor, manufacturing method thereof, and base substrate therefor
CN100401602C (en) * 2003-11-27 2008-07-09 中国科学院福建物质结构研究所 Zinc oxide bluish violet light semiconductor growth using liquid phase epitaxial method
JP5260881B2 (en) * 2007-03-20 2013-08-14 三菱瓦斯化学株式会社 Mg-containing ZnO mixed crystal single crystal, laminated body thereof, and production method thereof

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63144191A (en) * 1986-12-02 1988-06-16 Sumitomo Electric Ind Ltd Production of compound semiconductor single crystal and apparatus therefor
JP2000302596A (en) * 1999-04-15 2000-10-31 Fujikura Ltd Oxide superconductor and its production
JP2002009353A (en) * 2000-06-16 2002-01-11 Internatl Superconductivity Technology Center Bicrystal oxide superconducting film and high temperature superconducting josephson junction element and superconducting quantum inteference element using it
JP2003046081A (en) 2001-07-30 2003-02-14 Sharp Corp Semiconductor device
JP2005072067A (en) 2003-08-27 2005-03-17 National Institute For Materials Science Zinc oxide base multilayer structure and its fabricating process
JP2007100146A (en) 2005-09-30 2007-04-19 Dowa Holdings Co Ltd Cu-Ni-Sn-P-BASED COPPER ALLOY HAVING LESSENED ANISOTROPY OF STRESS RELAXATION RESISTANCE, AND MANUFACTURING METHOD THEREFOR
JP2007204324A (en) 2006-02-02 2007-08-16 Tokyo Denpa Co Ltd Manufacturing method of high purity zinc oxide single crystal, and high purity zinc oxide single crystal
JP2007223878A (en) * 2006-02-27 2007-09-06 Sumitomo Electric Ind Ltd Method for producing group iii nitride crystal and group iii nitride crystal substrate
WO2007100146A1 (en) * 2006-03-01 2007-09-07 Mitsubishi Gas Chemical Company, Inc. PROCESS FOR PRODUCING ZnO SINGLE CRYSTAL ACCORDING TO METHOD OF LIQUID PHASE GROWTH

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
A. OHTOMO ET AL., APPLIED PHYSICS LETTERS, vol. 72, no. 19, 11 May 1998 (1998-05-11), pages 2466 - 2468
H. RYOKEN ET AL., JOURNAL OF CRYSTAL GROWTH, vol. 287, 2006, pages 134 - 138
KOBAYASHI J. ET AL.: "Ekiso Epitaxy-ho ni yoru (Zn,Mg)O Komaku no Seicho", THE CERAMIC SOCIETY OF JAPAN 2008 NEN NENKAI KOEN YOKOSHU, 20 March 2008 (2008-03-20), pages 15, XP008142199 *
MAKI ET AL., JPN. J. APPL. PHYS., vol. 42, 2003, pages 75 - 77
MAKI, JPN. J. APPL. PHYS., vol. 42, 2003, pages 75 - 77
See also references of EP2267193A4 *

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